diff --git a/index.md b/index.md
index 6058d02..a11dc38 100644
--- a/index.md
+++ b/index.md
@@ -12,6 +12,7 @@ with at least [nvi](https://en.wikipedia.org/wiki/Nvi) 1.79 and
 
 Helpful documents:<br />
 - [Roman Zolotarev: Edit text with vi(1)](https://rgz.ee/vi.html)<br />
+- [Hugo Daniel: vi is not vim](https://hugodaniel.pt/posts/vi-is-not-vim/)<br />
 - [Jeff W: vi help](http://www.jeffw.com/vi/vi_help.txt)<br />
 - [Maarten Litmaath: vi reference](http://www.ungerhu.com/jxh/vi.html)<br />
 - [alphanrrrd: extremely concise cheatsheet](http://www.alphanrrrd.org/vi.html)<br />