diff --git a/README.md b/README.md
index 7831d63..e3cf440 100644
--- a/README.md
+++ b/README.md
@@ -16,6 +16,10 @@ This allows us not only to syncronize a local vdir with a CalDAV server, but
 also syncronize two CalDAV servers or two local vdirs.
 
 ## Rough list of things that need to be done
-  - implement CalDAVStorage and CardDAVStorage
+  - implement CalDAVStorage and CardDAVStorage --
+    While events generally have to be referenced by href, there's an example in
+    the [CalDAV RFC](http://www.ietf.org/rfc/rfc4791.txt) (Ctrl+F for "by UID")
+    on how to get events by UID. In the worst case we have to find out the href
+    through that every time we want to delete or update an event.
   - finish the CLI and decide on a config format
   - moar tests