diff --git a/ch2/notes.md b/ch2/notes.md
index 835687e..0dd3925 100644
--- a/ch2/notes.md
+++ b/ch2/notes.md
@@ -1,2 +1,3 @@
 * [什么是HTTP协议?](https://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol)
 * [RFC7230](https://tools.ietf.org/html/rfc7230#page-19)
+* [urllib和urllib2区别](http://ver007.com/2015/09/22/276.html)