diff --git a/readme.md b/readme.md
index 1ab2a51..bf6d80d 100644
--- a/readme.md
+++ b/readme.md
@@ -17,7 +17,7 @@ Intro.
 
 ## 3 What
 
-## 4 Who
+## 4 {#who} [Who](#toc)
 
 ### 4.1 Author