diff --git a/NOTES.md b/NOTES.md
index 8db04d9dd..9cf98e51c 100644
--- a/NOTES.md
+++ b/NOTES.md
@@ -18,6 +18,8 @@ In English:
 
 ## Persistence
 
+The background for this is in [#50](https://github.com/systemed/iD/issues/50).
+
 The idea is that we keep every _changed_ of an object around, but reuse
 unchanged objects between versions.