diff --git a/all/README.md b/all/README.md
index d49b0b0..dee506e 100644
--- a/all/README.md
+++ b/all/README.md
@@ -1,8 +1,8 @@
 # [@observable/all](https://jsr.io/@observable/all)
 
-[`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s an
+[Pushes](https://jsr.io/@observable/core#push) an
 [`Array`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array) of
-values from _all_ of the given `observables` in
+the latest values from _all_ of the given `observables` in
 [iteration](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#the_iterable_protocol)
 order.
 
@@ -88,6 +88,57 @@ all([]).subscribe({
 // "return"
 ```
 
+Iterable of observables
+
+```ts
+import { all } from "@observable/all";
+import { Subject } from "@observable/core";
+
+const subject1 = new Subject<number>();
+const subject2 = subject1;
+const subject3 = new Subject<number>();
+const controller = new AbortController();
+
+all(new Set([subject1, subject2, subject3])).subscribe({
+  signal: controller.signal,
+  next: (value) => console.log("next", value),
+  return: () => console.log("return"),
+  throw: (value) => console.log("throw", value),
+});
+
+subject2.next(1);
+subject1.next(2);
+subject3.next(3); // "next" [2, 3]
+subject1.next(4); // "next" [4, 3]
+subject2.next(5); // "next" [4, 5]
+subject1.return();
+subject3.return(); // "return"
+subject2.return();
+```
+
+Iterable with an empty observable
+
+```ts
+import { all } from "@observable/all";
+import { forOf } from "@observable/for-of";
+import { pipe } from "@observable/pipe";
+import { empty } from "@observable/empty";
+
+const observable1 = forOf([1, 2, 3]);
+const observable2 = forOf([7, 8, 9]);
+const controller = new AbortController();
+
+all(new Set([observable1, empty, observable2])).subscribe({
+  signal: controller.signal,
+  next: (value) => console.log("next", value),
+  return: () => console.log("return"),
+  throw: (value) => console.log("throw", value),
+});
+
+// Console output:
+// "return"
+```
+
 # AI Prompt
 
 Use the following prompt with AI assistants to help them understand this library:
diff --git a/all/deno.json b/all/deno.json
index e3f1987..035e0a4 100644
--- a/all/deno.json
+++ b/all/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/all",
-  "version": "0.15.0",
+  "version": "0.16.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/all/mod.ts b/all/mod.ts
index 1259b18..8e5a10f 100644
--- a/all/mod.ts
+++ b/all/mod.ts
@@ -11,7 +11,7 @@ import { takeUntil } from "@observable/take-until";
 import { finalize } from "@observable/finalize";
 
 /**
- * [`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s {@linkcode Values|values} from _all_ of the given
+ * [Pushes](https://jsr.io/@observable/core#push) the latest {@linkcode Values|values} from _all_ of the given
  * {@linkcode observables} in [index](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array#array_indices)
  * order.
  * @example
@@ -83,9 +83,9 @@ export function all<const Values extends ReadonlyArray<unknown>>(
   observables: Readonly<{ [Key in keyof Values]: Observable<Values[Key]> }>,
 ): Observable<Values>;
 /**
- * [`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s an [`Array`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array)
- * of {@linkcode Value|values} from _all_ of the given {@linkcode observables} in [iteration](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#the_iterable_protocol)
- * order.
+ * [Pushes](https://jsr.io/@observable/core#push) an [`Array`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array)
+ * of the latest {@linkcode Value|values} from _all_ of the given {@linkcode observables} in
+ * [iteration](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#the_iterable_protocol) order.
  * @example
  * Iterable of observables
  * ```ts
@@ -103,6 +103,7 @@ export function all<const Values extends ReadonlyArray<unknown>>(
  *   return: () => console.log("return"),
  *   throw: (value) => console.log("throw", value),
  * });
+ *
  * subject2.next(1);
  * subject1.next(2);
  * subject3.next(3); // "next" [2, 3]
diff --git a/async-await/README.md b/async-await/README.md
index 2344325..919bbf5 100644
--- a/async-await/README.md
+++ b/async-await/README.md
@@ -1,8 +1,7 @@
 # [@observable/async-await](https://jsr.io/@observable/async-await)
 
 [`Await`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await)s the
-given `expression`, [`next`](https://jsr.io/@observable/core/doc/~/Observer.next)s its resolved
-value, and then [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+given `expression` and [pushes](https://jsr.io/@observable/core#push) its resolved value.
 
 ## Build
 
diff --git a/async-await/deno.json b/async-await/deno.json
index 5aa19b3..6e6c289 100644
--- a/async-await/deno.json
+++ b/async-await/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/async-await",
-  "version": "0.4.0",
+  "version": "0.5.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/async-await/mod.ts b/async-await/mod.ts
index 217d659..f0c8114 100644
--- a/async-await/mod.ts
+++ b/async-await/mod.ts
@@ -2,8 +2,7 @@ import { Observable } from "@observable/core";
 
 /**
  * [`Await`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await)s the given
- * {@linkcode expression}, [`next`](https://jsr.io/@observable/core/doc/~/Observer.next)s its resolved value, and then
- * [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+ * {@linkcode expression} and [pushes](https://jsr.io/@observable/core#push) its resolved value.
  * @example
  * Resolved promise
  * ```ts
diff --git a/at/README.md b/at/README.md
index b6304d2..6e89221 100644
--- a/at/README.md
+++ b/at/README.md
@@ -1,8 +1,7 @@
 # [@observable/at](https://jsr.io/@observable/at)
 
-[`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s the first value at the given `index`
-and then [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s. Negative indices count
-back from the last value in the sequence.
+[Pushes](https://jsr.io/@observable/core#push) the first value at the given `index`. Negative
+indices count back from the last value in the sequence.
 
 ## Build
 
diff --git a/at/deno.json b/at/deno.json
index 3b468d6..4bb8c3a 100644
--- a/at/deno.json
+++ b/at/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/at",
-  "version": "0.6.0",
+  "version": "0.7.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/at/mod.ts b/at/mod.ts
index 0a456b8..fdb7d29 100644
--- a/at/mod.ts
+++ b/at/mod.ts
@@ -7,9 +7,8 @@ import { empty } from "@observable/empty";
 import { from } from "@observable/from";
 
 /**
- * [`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s the first {@linkcode Value|value} at the given
- * {@linkcode index} and then [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s. Negative
- * {@linkcode index|indices} count back from the last {@linkcode Value|value} in the sequence.
+ * [Pushes](https://jsr.io/@observable/core#push) the first {@linkcode Value|value} at the given
+ * {@linkcode index}. Negative {@linkcode index|indices} count back from the last {@linkcode Value|value} in the sequence.
  * @example
  * Positive index integer
  * ```ts
diff --git a/debounce/README.md b/debounce/README.md
index f4e6357..487c07c 100644
--- a/debounce/README.md
+++ b/debounce/README.md
@@ -1,6 +1,6 @@
 # [@observable/debounce](https://jsr.io/@observable/debounce)
 
-Debounces each value by the given number of `milliseconds`.
+Debounces each value by the given `milliseconds`.
 
 ## Build
 
diff --git a/debounce/deno.json b/debounce/deno.json
index 7da2d34..16d023a 100644
--- a/debounce/deno.json
+++ b/debounce/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/debounce",
-  "version": "0.17.0",
+  "version": "0.18.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/delay/README.md b/delay/README.md
index 6594cbb..65efb1c 100644
--- a/delay/README.md
+++ b/delay/README.md
@@ -1,6 +1,6 @@
 # [@observable/delay](https://jsr.io/@observable/delay)
 
-Delays values by the given number of `milliseconds`.
+Delays values by the given `milliseconds`.
 
 ## Build
 
diff --git a/delay/deno.json b/delay/deno.json
index 28e1f01..2a62050 100644
--- a/delay/deno.json
+++ b/delay/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/delay",
-  "version": "0.1.0",
+  "version": "0.2.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/delay/mod.ts b/delay/mod.ts
index 798b43a..3d74a25 100644
--- a/delay/mod.ts
+++ b/delay/mod.ts
@@ -8,7 +8,7 @@ import { drop } from "@observable/drop";
 import { from } from "@observable/from";
 
 /**
- * Delays {@linkcode Value|values} by the given number of {@linkcode milliseconds}.
+ * Delays {@linkcode Value|values} by the given {@linkcode milliseconds}.
  * @example
  * 1000 milliseconds
  * ```ts
diff --git a/distinct-until-changed/README.md b/distinct-until-changed/README.md
index 769e2c6..640ac4c 100644
--- a/distinct-until-changed/README.md
+++ b/distinct-until-changed/README.md
@@ -1,7 +1,7 @@
 # [@observable/distinct-until-changed](https://jsr.io/@observable/distinct-until-changed)
 
-Filters each value that is distinct from the previous value according to the given `comparator`
-function or
+[Pushes](https://jsr.io/@observable/core#push) each value that is distinct from the previous value
+according to the given `comparator` function or
 [`Object.is`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is)
 if one is not provided.
 
diff --git a/distinct-until-changed/deno.json b/distinct-until-changed/deno.json
index 89b7071..ebb0182 100644
--- a/distinct-until-changed/deno.json
+++ b/distinct-until-changed/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/distinct-until-changed",
-  "version": "0.16.0",
+  "version": "0.17.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/distinct-until-changed/mod.ts b/distinct-until-changed/mod.ts
index 7dd33a7..edc15c3 100644
--- a/distinct-until-changed/mod.ts
+++ b/distinct-until-changed/mod.ts
@@ -14,7 +14,8 @@ import { of } from "@observable/of";
 const noValue = Symbol("Flag indicating that no value has been emitted yet");
 
 /**
- * Filters each {@linkcode Value|value} that is [distinct](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is)
+ * [Pushes](https://jsr.io/@observable/core#push) each {@linkcode Value|value} that is
+ * [distinct](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is)
  * from the previous {@linkcode Value|value}.
  * @example
  * ```ts
@@ -40,7 +41,8 @@ const noValue = Symbol("Flag indicating that no value has been emitted yet");
  */
 export function distinctUntilChanged<Value>(): (source: Observable<Value>) => Observable<Value>;
 /**
- * Filters each {@linkcode Value|value} that is distinct from the previous {@linkcode Value|value} according to the given {@linkcode comparator} function.
+ * [Pushes](https://jsr.io/@observable/core#push) each {@linkcode Value|value} that is distinct from the previous
+ * {@linkcode Value|value} according to the given {@linkcode comparator} function.
  * @example
  * ```ts
  * import { distinctUntilChanged } from "@observable/distinct-until-changed";
@@ -66,8 +68,10 @@ export function distinctUntilChanged<Value>(
   comparator: (previous: Value, current: Value) => boolean,
 ): (source: Observable<Value>) => Observable<Value>;
 /**
- * Filters each {@linkcode Value|value} that is distinct from the previous {@linkcode Value|value} according to the given {@linkcode comparator}
- * function or [`Object.is`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is) if one is not provided.
+ * [Pushes](https://jsr.io/@observable/core#push) each {@linkcode Value|value} that is distinct from the previous
+ * {@linkcode Value|value} according to the given {@linkcode comparator} function or
+ * [`Object.is`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is) if one is
+ * not provided.
  * @example
  * Default comparator
  * ```ts
diff --git a/distinct/README.md b/distinct/README.md
index c8ebdc4..5ed709d 100644
--- a/distinct/README.md
+++ b/distinct/README.md
@@ -1,6 +1,6 @@
 # [@observable/distinct](https://jsr.io/@observable/distinct)
 
-Filters values that are
+[Pushes](https://jsr.io/@observable/core#push) values that are
 [distinct](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is)
 from all previous values.
 
diff --git a/distinct/deno.json b/distinct/deno.json
index 8ab61c4..3d789d3 100644
--- a/distinct/deno.json
+++ b/distinct/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/distinct",
-  "version": "0.13.0",
+  "version": "0.14.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/distinct/mod.ts b/distinct/mod.ts
index 8b04144..5fbf825 100644
--- a/distinct/mod.ts
+++ b/distinct/mod.ts
@@ -6,7 +6,8 @@ import { tap } from "@observable/tap";
 import { filter } from "@observable/filter";
 
 /**
- * Filters {@linkcode Value|values} that are [distinct](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is)
+ * [Pushes](https://jsr.io/@observable/core#push) {@linkcode Value|values} that are
+ * [distinct](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is)
  * from all previous {@linkcode Value|values}.
  * @example
  * ```ts
diff --git a/exhaust-map/README.md b/exhaust-map/README.md
index f025efd..4a353c8 100644
--- a/exhaust-map/README.md
+++ b/exhaust-map/README.md
@@ -1,8 +1,9 @@
 # [@observable/exhaust-map](https://jsr.io/@observable/exhaust-map)
 
 Projects each value to an [`Observable`](https://jsr.io/@observable/core/doc/~/Observable) ignoring
-any new values until the projected [`Observable`](https://jsr.io/@observable/core/doc/~/Observable)
-[`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+any new value until all values of the projected
+[`Observable`](https://jsr.io/@observable/core/doc/~/Observable) have been
+[pushed](https://jsr.io/@observable/core#push).
 
 ## Build
 
@@ -27,10 +28,9 @@ import { timeout } from "@observable/timeout";
 import { map } from "@observable/map";
 
 const controller = new AbortController();
-const observable = forOf([1, 2, 3]);
 
 pipe(
-  observable,
+  forOf([1, 2, 3]),
   exhaustMap((value) => pipe(timeout(100), map(() => value))),
 ).subscribe({
   signal: controller.signal,
diff --git a/exhaust-map/deno.json b/exhaust-map/deno.json
index 886b1d7..0c3af9f 100644
--- a/exhaust-map/deno.json
+++ b/exhaust-map/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/exhaust-map",
-  "version": "0.11.0",
+  "version": "0.12.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/exhaust-map/mod.ts b/exhaust-map/mod.ts
index 439c5ba..8fc2306 100644
--- a/exhaust-map/mod.ts
+++ b/exhaust-map/mod.ts
@@ -7,8 +7,8 @@ import { finalize } from "@observable/finalize";
 
 /**
  * {@linkcode project|Projects} each {@linkcode In|value} to an [`Observable`](https://jsr.io/@observable/core/doc/~/Observable) ignoring any new
- * {@linkcode In|values} until the {@linkcode project|projected} [`Observable`](https://jsr.io/@observable/core/doc/~/Observable)
- * [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+ * {@linkcode In|values} until all {@linkcode Out|values} of the {@linkcode project|projected} [`Observable`](https://jsr.io/@observable/core/doc/~/Observable)
+ * have been [pushed](https://jsr.io/@observable/core#push).
  * @example
  * ```ts
  * import { exhaustMap } from "@observable/exhaust-map";
@@ -18,10 +18,9 @@ import { finalize } from "@observable/finalize";
  * import { map } from "@observable/map";
  *
  * const controller = new AbortController();
- * const observable = forOf([1, 2, 3]);
  *
  * pipe(
- *   observable,
+ *   forOf([1, 2, 3]),
  *   exhaustMap((value) => pipe(timeout(100), map(() => value))),
  * ).subscribe({
  *   signal: controller.signal,
diff --git a/expand/README.md b/expand/README.md
index b6ce3fd..11b1c3b 100644
--- a/expand/README.md
+++ b/expand/README.md
@@ -1,7 +1,7 @@
 # [@observable/expand](https://jsr.io/@observable/expand)
 
-Recursively projects each value to an
-[`Observable`](https://jsr.io/@observable/core/doc/~/Observable).
+Projects each value to an [`Observable`](https://jsr.io/@observable/core/doc/~/Observable)
+recursively.
 
 ## Build
 
diff --git a/expand/deno.json b/expand/deno.json
index b81a5f6..c366758 100644
--- a/expand/deno.json
+++ b/expand/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/expand",
-  "version": "0.10.0",
+  "version": "0.11.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/expand/mod.ts b/expand/mod.ts
index 9e15761..42eb080 100644
--- a/expand/mod.ts
+++ b/expand/mod.ts
@@ -7,8 +7,8 @@ import { defer } from "@observable/defer";
 import { of } from "@observable/of";
 
 /**
- * Recursively {@linkcode project|projects} each {@linkcode Value|value} to an
- * [`Observable`](https://jsr.io/@observable/core/doc/~/Observable).
+ * {@linkcode project|Projects} each {@linkcode Value|value} to an
+ * [`Observable`](https://jsr.io/@observable/core/doc/~/Observable) recursively.
  * @example
  * Double until 16
  * ```ts
diff --git a/filter/README.md b/filter/README.md
index c9fe901..c2f5318 100644
--- a/filter/README.md
+++ b/filter/README.md
@@ -1,6 +1,6 @@
 # [@observable/filter](https://jsr.io/@observable/filter)
 
-Filters values that satisfy the given `predicate` function.
+[Pushes](https://jsr.io/@observable/core#push) values that satisfy the given `predicate` function.
 
 ## Build
 
diff --git a/filter/deno.json b/filter/deno.json
index bd8961b..e722d7a 100644
--- a/filter/deno.json
+++ b/filter/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/filter",
-  "version": "0.11.0",
+  "version": "0.12.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/filter/mod.ts b/filter/mod.ts
index 92f0e32..c87c680 100644
--- a/filter/mod.ts
+++ b/filter/mod.ts
@@ -2,7 +2,7 @@ import { isObservable, Observable } from "@observable/core";
 import { from } from "@observable/from";
 
 /**
- * Filters {@linkcode Value|values} that satisfy the given {@linkcode predicate} function.
+ * [Pushes](https://jsr.io/@observable/core#push) {@linkcode Value|values} that satisfy the given {@linkcode predicate} function.
  * @example
  * ```ts
  * import { filter } from "@observable/filter";
diff --git a/flat-map/README.md b/flat-map/README.md
index 70d5195..a3ae7df 100644
--- a/flat-map/README.md
+++ b/flat-map/README.md
@@ -1,9 +1,7 @@
 # [@observable/flat-map](https://jsr.io/@observable/flat-map)
 
-Sequentially projects each value to an
-[`Observable`](https://jsr.io/@observable/core/doc/~/Observable) waiting for each projected
-[`Observable`](https://jsr.io/@observable/core/doc/~/Observable) to
-[`return`](https://jsr.io/@observable/core/doc/~/Observer.return) before moving on to the next.
+Projects each value to an [`Observable`](https://jsr.io/@observable/core/doc/~/Observable)
+sequentially.
 
 ## Build
 
@@ -21,35 +19,44 @@ Run `deno task test` or `deno task test:ci` to execute the unit tests via
 ## Example
 
 ```ts
+import { Subject } from "@observable/core";
 import { flatMap } from "@observable/flat-map";
 import { forOf } from "@observable/for-of";
 import { pipe } from "@observable/pipe";
 
-const observable = forOf(["a", "b", "c"]);
 const controller = new AbortController();
 const observableLookup = {
-  a: forOf([1, 2, 3]),
-  b: forOf([4, 5, 6]),
-  c: forOf([7, 8, 9]),
+  a: new Subject<number>(),
+  b: new Subject<number>(),
+  c: new Subject<number>(),
 } as const;
 
-pipe(observable, flatMap((value) => observableLookup[value])).subscribe({
+pipe(forOf(["a", "b", "c"]), flatMap((value) => observableLookup[value])).subscribe({
   signal: controller.signal,
   next: (value) => console.log("next", value),
   return: () => console.log("return"),
   throw: (value) => console.log("throw", value),
 });
 
+observableLookup.b.next(1); // ignored
+observableLookup.a.next(2);
+observableLookup.a.next(3);
+observableLookup.a.return();
+observableLookup.c.next(4); // ignored
+observableLookup.b.next(5);
+observableLookup.b.next(6);
+observableLookup.b.return();
+observableLookup.c.next(7);
+observableLookup.c.next(8);
+observableLookup.c.return();
+
 // Console output:
-// "next" 1
 // "next" 2
 // "next" 3
-// "next" 4
 // "next" 5
 // "next" 6
 // "next" 7
 // "next" 8
-// "next" 9
 // "return"
 ```
 
diff --git a/flat-map/deno.json b/flat-map/deno.json
index 60a6d5f..ab3931f 100644
--- a/flat-map/deno.json
+++ b/flat-map/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/flat-map",
-  "version": "0.11.0",
+  "version": "0.12.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/flat-map/mod.ts b/flat-map/mod.ts
index ada45fb..d86def4 100644
--- a/flat-map/mod.ts
+++ b/flat-map/mod.ts
@@ -2,40 +2,47 @@ import { isObservable, Observable } from "@observable/core";
 import { from } from "@observable/from";
 
 /**
- * Sequentially {@linkcode project|projects} each {@linkcode In|value} to an [`Observable`](https://jsr.io/@observable/core/doc/~/Observable)
- * waiting for each {@linkcode project|projected} [`Observable`](https://jsr.io/@observable/core/doc/~/Observable)
- * to [`return`](https://jsr.io/@observable/core/doc/~/Observer.return) before moving on to the next.
+ * {@linkcode project|Projects} each {@linkcode In|value} to an [`Observable`](https://jsr.io/@observable/core/doc/~/Observable) sequentially.
  * @example
  * ```ts
+ * import { Subject } from "@observable/core";
  * import { flatMap } from "@observable/flat-map";
  * import { forOf } from "@observable/for-of";
  * import { pipe } from "@observable/pipe";
  *
- * const observable = forOf(["a", "b", "c"]);
  * const controller = new AbortController();
  * const observableLookup = {
- *   a: forOf([1, 2, 3]),
- *   b: forOf([4, 5, 6]),
- *   c: forOf([7, 8, 9]),
+ *   a: new Subject<number>(),
+ *   b: new Subject<number>(),
+ *   c: new Subject<number>(),
  * } as const;
  *
- * pipe(observable, flatMap((value) => observableLookup[value])).subscribe({
+ * pipe(forOf(["a", "b", "c"]), flatMap((value) => observableLookup[value])).subscribe({
  *   signal: controller.signal,
  *   next: (value) => console.log("next", value),
  *   return: () => console.log("return"),
  *   throw: (value) => console.log("throw", value),
  * });
  *
+ * observableLookup.b.next(1); // ignored
+ * observableLookup.a.next(2);
+ * observableLookup.a.next(3);
+ * observableLookup.a.return();
+ * observableLookup.c.next(4); // ignored
+ * observableLookup.b.next(5);
+ * observableLookup.b.next(6);
+ * observableLookup.b.return();
+ * observableLookup.c.next(7);
+ * observableLookup.c.next(8);
+ * observableLookup.c.return();
+ *
  * // Console output:
- * // "next" 1
  * // "next" 2
  * // "next" 3
- * // "next" 4
  * // "next" 5
  * // "next" 6
  * // "next" 7
  * // "next" 8
- * // "next" 9
  * // "return"
  * ```
  */
diff --git a/flat/README.md b/flat/README.md
index 5b4ddf8..84369e5 100644
--- a/flat/README.md
+++ b/flat/README.md
@@ -1,7 +1,8 @@
 # [@observable/flat](https://jsr.io/@observable/flat)
 
-Sequentially mirrors each given `observables` waiting for each one to
-[`return`](https://jsr.io/@observable/core/doc/~/Observer.return) before moving on to the next.
+[Pushes](https://jsr.io/@observable/core#push) _all_ values from each of the given `observables` in
+[iteration](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#the_iterable_protocol)
+order.
 
 ## Build
 
@@ -68,6 +69,35 @@ flat([]).subscribe({
 // "return"
 ```
 
+Iterable of observables
+
+```ts
+import { flat } from "@observable/flat";
+import { forOf } from "@observable/for-of";
+import { pipe } from "@observable/pipe";
+
+const controller = new AbortController();
+const observable1 = forOf([1, 2, 3]);
+const observable2 = observable1;
+const observable3 = forOf([4, 5, 6]);
+
+flat(new Set([observable1, observable2, observable3])).subscribe({
+  signal: controller.signal,
+  next: (value) => console.log("next", value),
+  return: () => console.log("return"),
+  throw: (value) => console.log("throw", value),
+});
+
+// Console output:
+// "next" 1
+// "next" 2
+// "next" 3
+// "next" 4
+// "next" 5
+// "next" 6
+// "return"
+```
+
 # AI Prompt
 
 Use the following prompt with AI assistants to help them understand this library:
diff --git a/flat/deno.json b/flat/deno.json
index 4066a90..fe4f9c0 100644
--- a/flat/deno.json
+++ b/flat/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/flat",
-  "version": "0.13.0",
+  "version": "0.14.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/flat/mod.ts b/flat/mod.ts
index cbd1992..d348c3a 100644
--- a/flat/mod.ts
+++ b/flat/mod.ts
@@ -5,8 +5,8 @@ import { flatMap } from "@observable/flat-map";
 import { empty } from "@observable/empty";
 
 /**
- * Sequentially mirrors each given {@linkcode observables} waiting for each one to [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)
- * before moving on to the next.
+ * [Pushes](https://jsr.io/@observable/core#push) _all_ values from each of the given {@linkcode observables} in
+ * [index](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array#array_indices) order.
  * @example
  * Array of observables
  * ```ts
@@ -60,10 +60,9 @@ export function flat<const Values extends ReadonlyArray<unknown>>(
   observables: Readonly<{ [Key in keyof Values]: Observable<Values[Key]> }>,
 ): Observable<Values[number]>;
 /**
- * Sequentially mirrors each given {@linkcode observables} waiting for each one to [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)
- * before moving on to the next.
+ * [Pushes](https://jsr.io/@observable/core#push) _all_ values from each of the given {@linkcode observables} in
+ * [iteration](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#the_iterable_protocol) order.
  * @example
- * Iterable of observables
  * ```ts
  * import { flat } from "@observable/flat";
  * import { forOf } from "@observable/for-of";
diff --git a/for-await-of/README.md b/for-await-of/README.md
index 00cf5c7..570ddf2 100644
--- a/for-await-of/README.md
+++ b/for-await-of/README.md
@@ -1,9 +1,8 @@
 # [@observable/for-await-of](https://jsr.io/@observable/for-await-of)
 
-[`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s each
+[Pushes](https://jsr.io/@observable/core#push) each
 [`await`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await)ed value
-of the given `values` in order and then
-[`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+of the given `values` in order.
 
 ## Build
 
diff --git a/for-await-of/deno.json b/for-await-of/deno.json
index 1c024d8..8c998f6 100644
--- a/for-await-of/deno.json
+++ b/for-await-of/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/for-await-of",
-  "version": "0.5.0",
+  "version": "0.6.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/for-await-of/mod.ts b/for-await-of/mod.ts
index 31e69ea..2b62899 100644
--- a/for-await-of/mod.ts
+++ b/for-await-of/mod.ts
@@ -1,8 +1,8 @@
 import { Observable } from "@observable/core";
 
 /**
- * [`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s each [`await`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await)ed
- * {@linkcode Value|value} of the given {@linkcode values} in order and then [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+ * [Pushes](https://jsr.io/@observable/core#push) each [`await`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await)ed
+ * {@linkcode Value|value} of the given {@linkcode values} in order.
  * @example
  * ```ts
  * import { forAwaitOf } from "@observable/for-await-of";
diff --git a/for-in/README.md b/for-in/README.md
index 7cd7272..917bfdd 100644
--- a/for-in/README.md
+++ b/for-in/README.md
@@ -1,7 +1,6 @@
 # [@observable/for-in](https://jsr.io/@observable/for-in)
 
-[`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s each key of the given `object` in
-order and then [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+[Pushes](https://jsr.io/@observable/core#push) each key of the given `object` in order.
 
 ## Build
 
diff --git a/for-in/deno.json b/for-in/deno.json
index b7e0bfa..88be87b 100644
--- a/for-in/deno.json
+++ b/for-in/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/for-in",
-  "version": "0.3.0",
+  "version": "0.4.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/for-in/mod.ts b/for-in/mod.ts
index bad1e87..8451f6c 100644
--- a/for-in/mod.ts
+++ b/for-in/mod.ts
@@ -1,8 +1,7 @@
 import { Observable } from "@observable/core";
 
 /**
- * [`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s each key of the given {@linkcode object} in order and then
- * [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+ * [Pushes](https://jsr.io/@observable/core#push) each key of the given {@linkcode object} in order.
  * @example
  * ```ts
  * import { forIn } from "@observable/for-in";
diff --git a/for-of/README.md b/for-of/README.md
index 19eafba..c1499c3 100644
--- a/for-of/README.md
+++ b/for-of/README.md
@@ -1,8 +1,8 @@
 # [@observable/for-of](https://jsr.io/@observable/for-of)
 
-[`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s each
+[Pushes](https://jsr.io/@observable/core#push) each
 [iterated](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols)
-value in order and then [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+value in order.
 
 ## Build
 
@@ -25,6 +25,7 @@ Populate array
 import { forOf } from "@observable/for-of";
 
 const controller = new AbortController();
+
 forOf([1, 2, 3]).subscribe({
   signal: controller.signal,
   next: (value) => console.log("next", value),
@@ -45,6 +46,7 @@ Empty array
 import { forOf } from "@observable/for-of";
 
 const controller = new AbortController();
+
 forOf([]).subscribe({
   signal: controller.signal,
   next: (value) => console.log("next", value),
@@ -62,6 +64,7 @@ Iterable
 import { forOf } from "@observable/for-of";
 
 const controller = new AbortController();
+
 forOf(new Set([1, 2, 1, 2, 3, 3])).subscribe({
   signal: controller.signal,
   next: (value) => console.log("next", value),
diff --git a/for-of/deno.json b/for-of/deno.json
index f9ebf5e..2c78c30 100644
--- a/for-of/deno.json
+++ b/for-of/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/for-of",
-  "version": "0.5.0",
+  "version": "0.6.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/for-of/mod.ts b/for-of/mod.ts
index e6d1507..b2afa2a 100644
--- a/for-of/mod.ts
+++ b/for-of/mod.ts
@@ -2,14 +2,15 @@ import { Observable } from "@observable/core";
 import { empty } from "@observable/empty";
 
 /**
- * [`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s each [iterated](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols)
- * value in order and then [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+ * [Pushes](https://jsr.io/@observable/core#push) each [iterated](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols)
+ * value in order.
  * @example
  * Populate array
  * ```ts
  * import { forOf } from "@observable/for-of";
  *
  * const controller = new AbortController();
+ *
  * forOf([1, 2, 3]).subscribe({
  *   signal: controller.signal,
  *   next: (value) => console.log("next", value),
@@ -29,6 +30,7 @@ import { empty } from "@observable/empty";
  * import { forOf } from "@observable/for-of";
  *
  * const controller = new AbortController();
+ *
  * forOf([]).subscribe({
  *   signal: controller.signal,
  *   next: (value) => console.log("next", value),
@@ -44,13 +46,14 @@ export function forOf<const Values extends ReadonlyArray<unknown>>(
   values: Values,
 ): Observable<Values[number]>;
 /**
- * [`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s each [iterated](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols)
- * {@linkcode Value|value} in order and then [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+ * [Pushes](https://jsr.io/@observable/core#push) each [iterated](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols)
+ * {@linkcode Value|value} in order.
  * @example
  * ```ts
  * import { forOf } from "@observable/for-of";
  *
  * const controller = new AbortController();
+ *
  * forOf(new Set([1, 2, 1, 2, 3, 3])).subscribe({
  *   signal: controller.signal,
  *   next: (value) => console.log("next", value),
diff --git a/interval/README.md b/interval/README.md
index 7bc67ca..9b5ebc1 100644
--- a/interval/README.md
+++ b/interval/README.md
@@ -1,7 +1,7 @@
 # [@observable/interval](https://jsr.io/@observable/interval)
 
-Repeatedly [`next`](https://jsr.io/@observable/core/doc/~/Observer.next)s a `void` value with a
-fixed time delay between each call.
+Repeatedly [pushes](https://jsr.io/@observable/core#push) a `void` value at an interval of the given
+`milliseconds`.
 
 ## Build
 
diff --git a/interval/deno.json b/interval/deno.json
index 1e45c9d..eda4ebd 100644
--- a/interval/deno.json
+++ b/interval/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/interval",
-  "version": "0.12.0",
+  "version": "0.13.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/interval/mod.ts b/interval/mod.ts
index d49fa11..8d64592 100644
--- a/interval/mod.ts
+++ b/interval/mod.ts
@@ -10,8 +10,7 @@ import { never } from "@observable/never";
 const infiniteVoid = defer(() => forOf(generateInfiniteVoid()));
 
 /**
- * Repeatedly [`next`](https://jsr.io/@observable/core/doc/~/Observer.next)s a `void` value with a
- * fixed {@linkcode milliseconds|time delay} between each call.
+ * Repeatedly [pushes](https://jsr.io/@observable/core#push) a `void` value at an interval of the given {@linkcode milliseconds}.
  * @example
  * Positive integer milliseconds
  * ```ts
diff --git a/last-value-from/README.md b/last-value-from/README.md
index 86ce098..51c7dca 100644
--- a/last-value-from/README.md
+++ b/last-value-from/README.md
@@ -1,8 +1,7 @@
 # [@observable/last-value-from](https://jsr.io/@observable/last-value-from)
 
 [`Resolve`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/resolve)s
-with the last value of the given `observable` on
-[`return`](https://jsr.io/@observable/core/doc/~/Observer.return),
+with the last value of the given `observable`,
 [`reject`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/reject)s
 with a [`throw`](https://jsr.io/@observable/core/doc/~/Observer.throw)n value of the given
 `observable`, or
@@ -10,7 +9,7 @@ with a [`throw`](https://jsr.io/@observable/core/doc/~/Observer.throw)n value of
 with a
 [`TypeError`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError)
 if the given `observable` [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s without
-[`next`](https://jsr.io/@observable/core/doc/~/Observer.next)ing a value.
+[pushing](https://jsr.io/@observable/core#push) a value.
 
 ## Build
 
diff --git a/last-value-from/deno.json b/last-value-from/deno.json
index f33cb54..5a91129 100644
--- a/last-value-from/deno.json
+++ b/last-value-from/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/last-value-from",
-  "version": "0.8.0",
+  "version": "0.9.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/last-value-from/mod.ts b/last-value-from/mod.ts
index 1b78be2..c245c74 100644
--- a/last-value-from/mod.ts
+++ b/last-value-from/mod.ts
@@ -4,13 +4,13 @@ import { at } from "@observable/at";
 
 /**
  * [`Resolve`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/resolve)s with the
- * last {@linkcode Value|value} of the given {@linkcode observable} on [`return`](https://jsr.io/@observable/core/doc/~/Observer.return),
+ * last {@linkcode Value|value} of the given {@linkcode observable},
  * [`reject`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/reject)s with
  * a [`throw`](https://jsr.io/@observable/core/doc/~/Observer.throw)n value of the given {@linkcode observable}, or
  * [`reject`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/reject)s with a
  * [`TypeError`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError)
  * if the given {@linkcode observable} [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s
- * without [`next`](https://jsr.io/@observable/core/doc/~/Observer.next)ing a {@linkcode Value|value}.
+ * without [pushing](https://jsr.io/@observable/core#push) a {@linkcode Value|value}.
  * @example
  * Last emitted value
  * ```ts
diff --git a/materialize/README.md b/materialize/README.md
index 61f9c1a..e90ad29 100644
--- a/materialize/README.md
+++ b/materialize/README.md
@@ -1,7 +1,9 @@
 # [@observable/materialize](https://jsr.io/@observable/materialize)
 
-[`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s all
-[notifications](https://jsr.io/@observable/core#notification) as values.
+[Pushes](https://jsr.io/@observable/core#push) all
+[notifications](https://jsr.io/@observable/core#notification) as values marked with their original
+types within
+[`ObserverNotification`](https://jsr.io/@observable/materialize/doc/~/ObserverNotification) objects.
 
 ## Build
 
diff --git a/materialize/deno.json b/materialize/deno.json
index fa4a906..bf0c69c 100644
--- a/materialize/deno.json
+++ b/materialize/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/materialize",
-  "version": "0.12.0",
+  "version": "0.13.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/materialize/mod.test.ts b/materialize/mod.test.ts
index 2946e6c..26a759d 100644
--- a/materialize/mod.test.ts
+++ b/materialize/mod.test.ts
@@ -1,9 +1,9 @@
-import { assertEquals } from "@std/assert";
+import { assertEquals, assertStrictEquals, assertThrows } from "@std/assert";
 import { Observer } from "@observable/core";
 import { forOf } from "@observable/for-of";
 import { pipe } from "@observable/pipe";
 import { throwError } from "@observable/throw-error";
-import { materialize, type ObserverNotification } from "./mod.ts";
+import { isObserverNotification, materialize, type ObserverNotification } from "./mod.ts";
 
 Deno.test(
   "materialize should emit the notifications from a source observable that returns",
@@ -90,3 +90,95 @@ Deno.test("materialize should honor unsubscription", () => {
   assertEquals(returnCalls, []);
   assertEquals(throwCalls, []);
 });
+
+Deno.test("isObserverNotification should throw if no arguments are provided", () => {
+  assertThrows(
+    // @ts-expect-error: Testing invalid arguments
+    () => isObserverNotification(),
+    TypeError,
+    "1 argument required but 0 present",
+  );
+});
+
+Deno.test("isObserverNotification should return true for a next notification", () => {
+  // Arrange
+  const notification: ObserverNotification = ["next", 0];
+
+  // Act
+  const result = isObserverNotification(notification);
+
+  // Assert
+  assertStrictEquals(result, true);
+});
+
+Deno.test("isObserverNotification should return true for a return notification", () => {
+  // Arrange
+  const notification: ObserverNotification = ["return"];
+
+  // Act
+  const result = isObserverNotification(notification);
+
+  // Assert
+  assertStrictEquals(result, true);
+});
+
+Deno.test("isObserverNotification should return true for a throw notification", () => {
+  // Arrange
+  const error = new Error("test");
+  const notification: ObserverNotification = ["throw", error];
+
+  // Act
+  const result = isObserverNotification(notification);
+
+  // Assert
+  assertStrictEquals(result, true);
+});
+
+Deno.test(
+  "isObserverNotification should return false when next lacks a value",
+  () => {
+    // Arrange
+    const notification = ["next"];
+
+    // Act
+    const result = isObserverNotification(notification);
+
+    // Assert
+    assertStrictEquals(result, false);
+  },
+);
+Deno.test(
+  "isObserverNotification should return false when throw lacks a value",
+  () => {
+    // Arrange
+    const notification = ["throw"];
+
+    // Act
+    const result = isObserverNotification(notification);
+
+    // Assert
+    assertStrictEquals(result, false);
+  },
+);
+
+Deno.test("isObserverNotification should return false for an unknown notification kind", () => {
+  // Arrange
+  const notification = ["invalid"];
+
+  // Act
+  const result = isObserverNotification(notification);
+
+  // Assert
+  assertStrictEquals(result, false);
+});
+
+Deno.test("isObserverNotification should return false when the value is not an array", () => {
+  // Arrange
+  const value = null;
+
+  // Act
+  const result = isObserverNotification(value);
+
+  // Assert
+  assertStrictEquals(result, false);
+});
diff --git a/materialize/mod.ts b/materialize/mod.ts
index 6d99fde..2a40fbd 100644
--- a/materialize/mod.ts
+++ b/materialize/mod.ts
@@ -12,7 +12,8 @@ export type ObserverNotification<Value = unknown> = Readonly<
 >;
 
 /**
- * [`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s all [notifications](https://jsr.io/@observable/core#notification) as values.
+ * [Pushes](https://jsr.io/@observable/core#push) all [notifications](https://jsr.io/@observable/core#notification)
+ * as values marked with their original types within {@linkcode ObserverNotification} objects.
  * @example
  * Notifications as values
  * ```ts
@@ -117,3 +118,66 @@ export function materialize<Value>(): (
     );
   };
 }
+
+/**
+ * Checks if a {@linkcode value} is an object that implements the {@linkcode ObserverNotification} interface.
+ * @example
+ * Next
+ * ```ts
+ * import { isObserverNotification, ObserverNotification } from "@observable/materialize";
+ *
+ * const value: ObserverNotification = ["next", 1];
+ *
+ * isObserverNotification(value); // true
+ * ```
+ * @example
+ * Return
+ * ```ts
+ * import { isObserverNotification, ObserverNotification } from "@observable/materialize";
+ *
+ * const value: ObserverNotification = ["return"];
+ *
+ * isObserverNotification(value); // true
+ * ```
+ * @example
+ * Throw
+ * ```ts
+ * import { isObserverNotification, ObserverNotification } from "@observable/materialize";
+ *
+ * const value: ObserverNotification = ["throw", new Error("error")];
+ *
+ * isObserverNotification(value); // true
+ * ```
+ * @example
+ * Invalid Next
+ * ```ts
+ * import { isObserverNotification, ObserverNotification } from "@observable/materialize";
+ *
+ * const value: ObserverNotification = ["next"];
+ *
+ * isObserverNotification(value); // false
+ * ```
+ * @example
+ * Invalid Throw
+ * ```ts
+ * import { isObserverNotification, ObserverNotification } from "@observable/materialize";
+ *
+ * const value: ObserverNotification = ["throw"];
+ *
+ * isObserverNotification(value); // false
+ * ```
+ * @example
+ * Invalid
+ * ```ts
+ * import { isObserverNotification, ObserverNotification } from "@observable/materialize";
+ *
+ * const value = ["invalid"];
+ *
+ * isObserverNotification(value); // false
+ * ```
+ */
+export function isObserverNotification(value: unknown): value is ObserverNotification {
+  if (!arguments.length) throw new TypeError("1 argument required but 0 present");
+  return Array.isArray(value) &&
+    (value[0] === "return" || ((value[0] === "next" || value[0] === "throw") && value.length > 1));
+}
diff --git a/merge-map/README.md b/merge-map/README.md
index 59c3a09..2dd48ca 100644
--- a/merge-map/README.md
+++ b/merge-map/README.md
@@ -1,7 +1,7 @@
 # [@observable/merge-map](https://jsr.io/@observable/merge-map)
 
-Concurrently projects each value to an
-[`Observable`](https://jsr.io/@observable/core/doc/~/Observable).
+Projects each value to an [`Observable`](https://jsr.io/@observable/core/doc/~/Observable)
+concurrently.
 
 ## Build
 
@@ -19,26 +19,37 @@ Run `deno task test` or `deno task test:ci` to execute the unit tests via
 ## Example
 
 ```ts
+import { Subject } from "@observable/core";
 import { mergeMap } from "@observable/merge-map";
 import { forOf } from "@observable/for-of";
 import { pipe } from "@observable/pipe";
 
 const controller = new AbortController();
 const observableLookup = {
-  1: forOf([1, 2, 3]),
-  2: forOf([4, 5, 6]),
-  3: forOf([7, 8, 9]),
+  a: new Subject<number>(),
+  b: new Subject<number>(),
+  c: new Subject<number>(),
 } as const;
-pipe(
-  forOf([1, 2, 3]),
-  mergeMap((value) => observableLookup[value]),
-).subscribe({
+
+pipe(forOf(["a", "b", "c"]), mergeMap((value) => observableLookup[value])).subscribe({
   signal: controller.signal,
   next: (value) => console.log("next", value),
   return: () => console.log("return"),
   throw: (value) => console.log("throw", value),
 });
 
+observableLookup.b.next(1);
+observableLookup.a.next(2);
+observableLookup.a.next(3);
+observableLookup.a.return();
+observableLookup.c.next(4);
+observableLookup.b.next(5);
+observableLookup.b.next(6);
+observableLookup.b.return();
+observableLookup.c.next(7);
+observableLookup.c.next(8);
+observableLookup.c.return();
+
 // Console output:
 // "next" 1
 // "next" 2
@@ -48,7 +59,6 @@ pipe(
 // "next" 6
 // "next" 7
 // "next" 8
-// "next" 9
 // "return"
 ```
 
diff --git a/merge-map/deno.json b/merge-map/deno.json
index f76da9c..e991396 100644
--- a/merge-map/deno.json
+++ b/merge-map/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/merge-map",
-  "version": "0.14.0",
+  "version": "0.15.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/merge-map/mod.ts b/merge-map/mod.ts
index e8de3ed..53529a3 100644
--- a/merge-map/mod.ts
+++ b/merge-map/mod.ts
@@ -2,27 +2,40 @@ import { isObservable, Observable } from "@observable/core";
 import { from } from "@observable/from";
 
 /**
- * Concurrently {@linkcode project|projects} each {@linkcode In|value} to an
- * [`Observable`](https://jsr.io/@observable/core/doc/~/Observable).
+ * {@linkcode project|Projects} each {@linkcode In|value} to an [`Observable`](https://jsr.io/@observable/core/doc/~/Observable) concurrently.
  * @example
  * ```ts
+ * import { Subject } from "@observable/core";
  * import { mergeMap } from "@observable/merge-map";
  * import { forOf } from "@observable/for-of";
  * import { pipe } from "@observable/pipe";
  *
  * const controller = new AbortController();
  * const observableLookup = {
- *   1: forOf([1, 2, 3]),
- *   2: forOf([4, 5, 6]),
- *   3: forOf([7, 8, 9]),
+ *   a: new Subject<number>(),
+ *   b: new Subject<number>(),
+ *   c: new Subject<number>(),
  * } as const;
- * pipe(forOf([1, 2, 3]), mergeMap((value) => observableLookup[value])).subscribe({
+ *
+ * pipe(forOf(["a", "b", "c"]), mergeMap((value) => observableLookup[value])).subscribe({
  *   signal: controller.signal,
  *   next: (value) => console.log("next", value),
  *   return: () => console.log("return"),
  *   throw: (value) => console.log("throw", value),
  * });
  *
+ * observableLookup.b.next(1);
+ * observableLookup.a.next(2);
+ * observableLookup.a.next(3);
+ * observableLookup.a.return();
+ * observableLookup.c.next(4);
+ * observableLookup.b.next(5);
+ * observableLookup.b.next(6);
+ * observableLookup.b.return();
+ * observableLookup.c.next(7);
+ * observableLookup.c.next(8);
+ * observableLookup.c.return();
+ *
  * // Console output:
  * // "next" 1
  * // "next" 2
@@ -32,7 +45,6 @@ import { from } from "@observable/from";
  * // "next" 6
  * // "next" 7
  * // "next" 8
- * // "next" 9
  * // "return"
  * ```
  */
diff --git a/merge/README.md b/merge/README.md
index 516f4f5..72e9c59 100644
--- a/merge/README.md
+++ b/merge/README.md
@@ -1,6 +1,6 @@
 # [@observable/merge](https://jsr.io/@observable/merge)
 
-Concurrently mirrors all of the given `observables`
+[Pushes](https://jsr.io/@observable/core#push) each value of the given `observables`.
 
 ## Build
 
diff --git a/merge/deno.json b/merge/deno.json
index 9445fa4..af63c19 100644
--- a/merge/deno.json
+++ b/merge/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/merge",
-  "version": "0.13.0",
+  "version": "0.14.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/merge/mod.ts b/merge/mod.ts
index a596025..106584d 100644
--- a/merge/mod.ts
+++ b/merge/mod.ts
@@ -5,7 +5,7 @@ import { mergeMap } from "@observable/merge-map";
 import { empty } from "@observable/empty";
 
 /**
- * Concurrently mirrors all of the given {@linkcode observables}.
+ * [Pushes](https://jsr.io/@observable/core#push) each value of the given {@linkcode observables}.
  * @example
  * Array of observables
  * ```ts
@@ -54,8 +54,7 @@ export function merge<const Values extends ReadonlyArray<unknown>>(
   observables: Readonly<{ [Key in keyof Values]: Observable<Values[Key]> }>,
 ): Observable<Values[number]>;
 /**
- * Concurrently [`next`](https://jsr.io/@observable/core/doc/~/Observer.next)s all values from all
- * given {@linkcode observables}.
+ * [Pushes](https://jsr.io/@observable/core#push) each {@linkcode Value|value} of the given {@linkcode observables}.
  * @example
  * Iterable of observables
  * ```ts
diff --git a/of/README.md b/of/README.md
index 988b34a..3673a45 100644
--- a/of/README.md
+++ b/of/README.md
@@ -1,7 +1,6 @@
 # [@observable/of](https://jsr.io/@observable/of)
 
-[`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s the given `value` and then
-[`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+[Pushes](https://jsr.io/@observable/core#push) the given `value`.
 
 ## Build
 
diff --git a/of/deno.json b/of/deno.json
index 533da22..70b1cd3 100644
--- a/of/deno.json
+++ b/of/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/of",
-  "version": "0.11.0",
+  "version": "0.12.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/of/mod.ts b/of/mod.ts
index 774f60c..bb8dc10 100644
--- a/of/mod.ts
+++ b/of/mod.ts
@@ -2,8 +2,7 @@ import type { Observable } from "@observable/core";
 import { forOf } from "@observable/for-of";
 
 /**
- * [`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s the given {@linkcode value}
- * and then [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+ * [Pushes](https://jsr.io/@observable/core#push) the given {@linkcode value}.
  * @example
  * ```ts
  * import { of } from "@observable/of";
diff --git a/pairwise/README.md b/pairwise/README.md
index 45f8796..319f1bd 100644
--- a/pairwise/README.md
+++ b/pairwise/README.md
@@ -1,6 +1,6 @@
 # [@observable/pairwise](https://jsr.io/@observable/pairwise)
 
-[`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s
+[Pushes](https://jsr.io/@observable/core#push)
 [`pair`](https://jsr.io/@observable/pairwise/doc/~/Pair)s of consecutive values.
 
 ## Build
diff --git a/pairwise/deno.json b/pairwise/deno.json
index 234e222..615245b 100644
--- a/pairwise/deno.json
+++ b/pairwise/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/pairwise",
-  "version": "0.14.0",
+  "version": "0.15.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/pairwise/mod.ts b/pairwise/mod.ts
index 2eb6e0a..2b17c43 100644
--- a/pairwise/mod.ts
+++ b/pairwise/mod.ts
@@ -15,7 +15,7 @@ const noValue = Symbol("Flag indicating that no value has been emitted yet");
 export type Pair<Value = unknown> = Readonly<[previous: Value, current: Value]>;
 
 /**
- * [`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s {@linkcode Pair|pair}s of consecutive {@linkcode Value|values}.
+ * [Pushes](https://jsr.io/@observable/core#push) {@linkcode Pair|pairs} of consecutive {@linkcode Value|values}.
  * @example
  * ```ts
  * import { pairwise } from "@observable/pairwise";
diff --git a/race/README.md b/race/README.md
index 7c3c851..661f9c4 100644
--- a/race/README.md
+++ b/race/README.md
@@ -1,8 +1,7 @@
 # [@observable/race](https://jsr.io/@observable/race)
 
-Mirrors the first of the given `observables` to
-[`next`](https://jsr.io/@observable/core/doc/~/Observer.next) or
-[`throw`](https://jsr.io/@observable/core/doc/~/Observer.throw) a value.
+[Pushes](https://jsr.io/@observable/core#push) values from the first of the given `observables` to
+[push](https://jsr.io/@observable/core#push) a value.
 
 ## Build
 
diff --git a/race/deno.json b/race/deno.json
index e9efbe9..7cf039c 100644
--- a/race/deno.json
+++ b/race/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/race",
-  "version": "0.15.0",
+  "version": "0.16.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/race/mod.ts b/race/mod.ts
index 8d9c36d..6f4f9f1 100644
--- a/race/mod.ts
+++ b/race/mod.ts
@@ -9,9 +9,7 @@ import { filter } from "@observable/filter";
 import { empty } from "@observable/empty";
 
 /**
- * Mirrors the first of the given {@linkcode observables} to
- * [`next`](https://jsr.io/@observable/core/doc/~/Observer.next) or
- * [`throw`](https://jsr.io/@observable/core/doc/~/Observer.throw) a value.
+ * [Pushes](https://jsr.io/@observable/core#push) values from the first of the given {@linkcode observables} to [push](https://jsr.io/@observable/core#push) a value.
  * @example
  * Array of observables
  * ```ts
@@ -59,9 +57,7 @@ export function race<const Values extends ReadonlyArray<unknown>>(
   observables: Readonly<{ [Key in keyof Values]: Observable<Values[Key]> }>,
 ): Observable<Values[number]>;
 /**
- * Mirrors the first of the given {@linkcode observables} to
- * [`next`](https://jsr.io/@observable/core/doc/~/Observer.next) or
- * [`throw`](https://jsr.io/@observable/core/doc/~/Observer.throw) a value.
+ * [Pushes](https://jsr.io/@observable/core#push) values from the first of the given {@linkcode observables} to [push](https://jsr.io/@observable/core#push) a value.
  * @example
  * Iterable of observables
  * ```ts
diff --git a/reduce/README.md b/reduce/README.md
index e3b4cc1..410d177 100644
--- a/reduce/README.md
+++ b/reduce/README.md
@@ -1,7 +1,6 @@
 # [@observable/reduce](https://jsr.io/@observable/reduce)
 
-Reduces each value to a single value on
-[`return`](https://jsr.io/@observable/core/doc/~/Observer.return).
+Reduces all values to a single values.
 
 ## Build
 
diff --git a/reduce/deno.json b/reduce/deno.json
index 60e2c8d..8008cba 100644
--- a/reduce/deno.json
+++ b/reduce/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/reduce",
-  "version": "0.11.0",
+  "version": "0.12.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/reduce/mod.ts b/reduce/mod.ts
index 217d6d9..3c5fe95 100644
--- a/reduce/mod.ts
+++ b/reduce/mod.ts
@@ -4,8 +4,7 @@ import { pipe } from "@observable/pipe";
 import { at } from "@observable/at";
 
 /**
- * {@linkcode reducer|Reduces} each {@linkcode In|value} to a single {@linkcode Out|value} on
- * [`return`](https://jsr.io/@observable/core/doc/~/Observer.return).
+ * {@linkcode reducer|Reduces} all {@linkcode In|values} to a single {@linkcode Out|value}.
  * @example
  * ```ts
  * import { reduce } from "@observable/reduce";
diff --git a/repeat/README.md b/repeat/README.md
index c86db50..4c22dc5 100644
--- a/repeat/README.md
+++ b/repeat/README.md
@@ -2,7 +2,7 @@
 
 Re-[`subscribe`](https://jsr.io/@observable/core/doc/~/Observable.subscribe)s on
 [`return`](https://jsr.io/@observable/core/doc/~/Observer.return) as long as the given `notifier`
-then [`next`](https://jsr.io/@observable/core/doc/~/Observer.next)s a value.
+then [pushes](https://jsr.io/@observable/core#push) a value.
 
 ## Build
 
diff --git a/repeat/deno.json b/repeat/deno.json
index 167ba49..8252cbf 100644
--- a/repeat/deno.json
+++ b/repeat/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/repeat",
-  "version": "0.13.0",
+  "version": "0.14.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/repeat/mod.ts b/repeat/mod.ts
index 61eac51..f5dbc80 100644
--- a/repeat/mod.ts
+++ b/repeat/mod.ts
@@ -9,7 +9,7 @@ import { of } from "@observable/of";
 /**
  * Re-[`subscribe`](https://jsr.io/@observable/core/doc/~/Observable.subscribe)s on
  * [`return`](https://jsr.io/@observable/core/doc/~/Observer.return) as long as the given {@linkcode notifier}
- * then [`next`](https://jsr.io/@observable/core/doc/~/Observer.next)s a value.
+ * then [pushes](https://jsr.io/@observable/core#push) a value.
  * @example
  * ```ts
  * import { repeat } from "@observable/repeat";
diff --git a/scan/README.md b/scan/README.md
index 54c981e..0d13ca1 100644
--- a/scan/README.md
+++ b/scan/README.md
@@ -1,6 +1,6 @@
 # [@observable/scan](https://jsr.io/@observable/scan)
 
-Reduces each value to a single value.
+Reduces each value to an intermediate value.
 
 ## Build
 
diff --git a/scan/deno.json b/scan/deno.json
index a1e81da..9ffd358 100644
--- a/scan/deno.json
+++ b/scan/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/scan",
-  "version": "0.10.0",
+  "version": "0.11.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/scan/mod.ts b/scan/mod.ts
index ed11608..a1208c8 100644
--- a/scan/mod.ts
+++ b/scan/mod.ts
@@ -5,7 +5,7 @@ import { pipe } from "@observable/pipe";
 import { map } from "@observable/map";
 
 /**
- * {@linkcode reducer|Reduces} each {@linkcode In|value} to a single {@linkcode Out|value}.
+ * {@linkcode reducer|Reduces} each {@linkcode In|value} to an intermediate {@linkcode Out|value}.
  * @example
  * ```ts
  * import { scan } from "@observable/scan";
diff --git a/take-until/README.md b/take-until/README.md
index 2957ed8..bdafde6 100644
--- a/take-until/README.md
+++ b/take-until/README.md
@@ -1,7 +1,7 @@
 # [@observable/take-until](https://jsr.io/@observable/take-until)
 
-Takes values until the given `notifier`
-[`next`](https://jsr.io/@observable/core/doc/~/Observer.next)s a value.
+[Pushes](https://jsr.io/@observable/core#push) values until the given `notifier` also
+[pushes](https://jsr.io/@observable/core#push) a value.
 
 ## Build
 
diff --git a/take-until/deno.json b/take-until/deno.json
index 8335ee9..557b8a0 100644
--- a/take-until/deno.json
+++ b/take-until/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/take-until",
-  "version": "0.12.0",
+  "version": "0.13.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/take-until/mod.ts b/take-until/mod.ts
index 5fb355b..8110df1 100644
--- a/take-until/mod.ts
+++ b/take-until/mod.ts
@@ -2,8 +2,8 @@ import { isObservable, Observable } from "@observable/core";
 import { from } from "@observable/from";
 
 /**
- * Takes {@linkcode Value|values} until the given {@linkcode notifier}
- * [`next`](https://jsr.io/@observable/core/doc/~/Observer.next)s a value.
+ * [Pushes](https://jsr.io/@observable/core#push) {@linkcode Value|values} until the given {@linkcode notifier}
+ * also [pushes](https://jsr.io/@observable/core#push) a value.
  * @example
  * ```ts
  * import { Subject } from "@observable/core";
diff --git a/take/README.md b/take/README.md
index c96d562..f2fd7a9 100644
--- a/take/README.md
+++ b/take/README.md
@@ -1,7 +1,6 @@
 # [@observable/take](https://jsr.io/@observable/take)
 
-Takes the first `count` of values and then
-[`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+[Pushes](https://jsr.io/@observable/core#push) the first of the given `count` of values.
 
 ## Build
 
diff --git a/take/deno.json b/take/deno.json
index 1422763..31bd33e 100644
--- a/take/deno.json
+++ b/take/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/take",
-  "version": "0.14.0",
+  "version": "0.15.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/take/mod.ts b/take/mod.ts
index cda505a..f62b2eb 100644
--- a/take/mod.ts
+++ b/take/mod.ts
@@ -3,7 +3,7 @@ import { from } from "@observable/from";
 import { empty } from "@observable/empty";
 
 /**
- * Takes the first {@linkcode count} of {@linkcode Value|values} and then [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+ * [Pushes](https://jsr.io/@observable/core#push) the first of the given {@linkcode count} of {@linkcode Value|values}.
  * @example
  * Positive integer count
  * ```ts
diff --git a/throttle/README.md b/throttle/README.md
index 9f033e9..b9b1271 100644
--- a/throttle/README.md
+++ b/throttle/README.md
@@ -1,6 +1,6 @@
 # [@observable/throttle](https://jsr.io/@observable/throttle)
 
-Throttles each value by the given number of `milliseconds`.
+Throttles each value by the given `milliseconds`.
 
 ## Build
 
diff --git a/throttle/deno.json b/throttle/deno.json
index a22a121..fad5715 100644
--- a/throttle/deno.json
+++ b/throttle/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/throttle",
-  "version": "0.17.0",
+  "version": "0.18.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/timeout/README.md b/timeout/README.md
index 86db5e6..01c0b6e 100644
--- a/timeout/README.md
+++ b/timeout/README.md
@@ -1,7 +1,6 @@
 # [@observable/timeout](https://jsr.io/@observable/timeout)
 
-[`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s a `void` value after the given number
-of `milliseconds` and then [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+[Pushes](https://jsr.io/@observable/core#push) a `void` value after the given `milliseconds`.
 
 ## Build
 
diff --git a/timeout/deno.json b/timeout/deno.json
index 3ad9c41..a848555 100644
--- a/timeout/deno.json
+++ b/timeout/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@observable/timeout",
-  "version": "0.12.0",
+  "version": "0.13.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }
diff --git a/timeout/mod.ts b/timeout/mod.ts
index 9cf7a58..b40bf95 100644
--- a/timeout/mod.ts
+++ b/timeout/mod.ts
@@ -6,8 +6,7 @@ import { pipe } from "@observable/pipe";
 import { take } from "@observable/take";
 
 /**
- * [`Next`](https://jsr.io/@observable/core/doc/~/Observer.next)s a `void` value after the given number of
- * {@linkcode milliseconds} and then [`return`](https://jsr.io/@observable/core/doc/~/Observer.return)s.
+ * [Pushes](https://jsr.io/@observable/core#push) a `void` value after the given {@linkcode milliseconds}.
  * @example
  * Positive integer milliseconds
  * ```ts