diff --git a/NOTES.md b/NOTES.md
index 67d7be2..b4d3d88 100644
--- a/NOTES.md
+++ b/NOTES.md
@@ -1,3 +1,3 @@
 Documentation for graph-easy, which is used to convert diag_inp.txt to
 the outputs, diag.*:
-http://bloodgate.com/perl/graph/manual/index.html
+https://web.archive.org/web/20200120140454/http://bloodgate.com/perl/graph/manual/index.html