diff --git a/README.md b/README.md
index 0c219ba..101d1be 100644
--- a/README.md
+++ b/README.md
@@ -82,3 +82,7 @@ OS X only). The code is portable and should run on any Common Lisp environment.
 ## TO DO
 
 Detailed documentation is yet to be written
+
+---
+
+upstream: https://github.com/2old2randr/cl-dates