diff --git a/os/linux/nixos/tools/dependency/articles.txt b/os/linux/nixos/tools/dependency/articles.txt
index 5aa8111ae..d7d1cce47 100644
--- a/os/linux/nixos/tools/dependency/articles.txt
+++ b/os/linux/nixos/tools/dependency/articles.txt
@@ -1,2 +1,4 @@
 2020
 https://rgoswami.me/posts/ccon-tut-nix/
+????
+https://www.reddit.com/r/NixOS/comments/19fafrg/how_to_install_a_previous_version_of_a_package/