diff --git a/javascript/sleep-for-a-bit-in-async-code.md b/javascript/sleep-for-a-bit-in-async-code.md
index 6f2b683..89bbdea 100644
--- a/javascript/sleep-for-a-bit-in-async-code.md
+++ b/javascript/sleep-for-a-bit-in-async-code.md
@@ -32,3 +32,5 @@ async function fakeUserFetch(userId) {
   return Promise.resolve(fakeResponse)
 }
 ```
+
+[source](https://stackoverflow.com/a/951057/535590)