diff --git a/README.md b/README.md
index 60b1445..fdda08f 100644
--- a/README.md
+++ b/README.md
@@ -559,7 +559,7 @@ But don't forget to do coding problems from above while you learn!
 - There are a lot of videos here. Just watch enough until you understand it. You can always come back and review.
 - Don't worry if you don't understand all the math behind it.
 - You just need to understand how to express the complexity of an algorithm in terms of Big-O.
-- [ ] [Harvard CS50 - Asymptotic Notation (video)](https://www.youtube.com/watch?v=iOq5kSKqeR4)
+- [X] [Harvard CS50 - Asymptotic Notation (video)](https://www.youtube.com/watch?v=iOq5kSKqeR4)
 - [ ] [Big O Notations (general quick tutorial) (video)](https://www.youtube.com/watch?v=V6mKVRU1evU)
 - [ ] [Big O Notation (and Omega and Theta) - best mathematical explanation (video)](https://www.youtube.com/watch?v=ei-A_wy5Yxw&index=2&list=PL1BaGV1cIH4UhkL8a9bJGG356covJ76qN)
 - [ ] [Skiena (video)](https://www.youtube.com/watch?v=z1mkCe3kVUA)