diff --git a/README.md b/README.md
index c54ce31..1273686 100644
--- a/README.md
+++ b/README.md
@@ -484,7 +484,7 @@ Write code on a whiteboard or paper, not a computer. Test with some sample input
 - [ ] [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=gSyDMtdPNpU&index=2&list=PLOtl7M3yp-DV69F32zdK7YJcNXpTunF2b)
-    - [slides](http://www3.cs.stonybrook.edu/~algorith/video-lectures/2007/lecture2.pdf)
+    - [slides](https://archive.org/details/lecture2_202008)
 - [ ] [A Gentle Introduction to Algorithm Complexity Analysis](http://discrete.gr/complexity/)
 - [ ] [Orders of Growth (video)](https://www.coursera.org/lecture/algorithmic-thinking-1/orders-of-growth-6PKkX)
 - [ ] [Asymptotics (video)](https://www.coursera.org/lecture/algorithmic-thinking-1/asymptotics-bXAtM)