diff --git a/02/concurrency/Makefile b/02/concurrency/Makefile
index 5fc9407..3951239 100644
--- a/02/concurrency/Makefile
+++ b/02/concurrency/Makefile
@@ -2,11 +2,11 @@ all: threads threads-notv
 
 CFLAGS=-fcf-protection=none -fno-asynchronous-unwind-tables -m32 -fno-pie -no-pie 
 
-threads: threads.c common.h common_threads.h
+threads: threads.c common_threads.h
 	gcc $(CFLAGS) -m32 -O1 -S threads.c
 	gcc $(CFLAGS) -m32 -o threads threads.s -Wall -pthread
 
-threads-notv: threads-notv.c common.h common_threads.h
+threads-notv: threads-notv.c common_threads.h
 	gcc $(CFLAGS) -m32 -O1 -S threads-notv.c
 	gcc $(CFLAGS) -m32 -o threads-notv threads-notv.s -Wall -pthread
 
diff --git a/02/concurrency/common.h b/02/concurrency/common.h
deleted file mode 100644
index 199b622..0000000
--- a/02/concurrency/common.h
+++ /dev/null
@@ -1,22 +0,0 @@
-#ifndef __common_h__
-#define __common_h__
-
-#include <stddef.h>
-#include <sys/time.h>
-#include <sys/stat.h>
-#include <assert.h>
-
-double GetTime() {
-    struct timeval t;
-    int rc = gettimeofday(&t, NULL);
-    assert(rc == 0);
-    return (double) t.tv_sec + (double) t.tv_usec/1e6;
-}
-
-void Spin(int howlong) {
-    double t = GetTime();
-    while ((GetTime() - t) < (double) howlong)
-	; // do nothing in loop
-}
-
-#endif // __common_h__
diff --git a/02/concurrency/threads-notv.c b/02/concurrency/threads-notv.c
index e629273..afd2e4e 100644
--- a/02/concurrency/threads-notv.c
+++ b/02/concurrency/threads-notv.c
@@ -1,6 +1,5 @@
 #include <stdio.h>
 #include <stdlib.h>
-#include "common.h"
 #include "common_threads.h"
 
 int counter = 0; 
@@ -16,7 +15,7 @@ void *worker(void *arg) {
 
 int main(int argc, char *argv[]) {
 	if (argc != 2) { 
-		fprintf(stderr, "usage: threads <loops>\n"); 
+		fprintf(stderr, "usage: threads-notv <loops>\n"); 
 		exit(1); 
 	} 
 	loops = atoi(argv[1]);
diff --git a/02/concurrency/threads.c b/02/concurrency/threads.c
index cdcd2b2..7a68cda 100644
--- a/02/concurrency/threads.c
+++ b/02/concurrency/threads.c
@@ -1,6 +1,5 @@
 #include <stdio.h>
 #include <stdlib.h>
-#include "common.h"
 #include "common_threads.h"
 
 volatile int counter = 0;