diff --git a/tasks.yml b/tasks.yml
index 3e46abb..58aed6e 100644
--- a/tasks.yml
+++ b/tasks.yml
@@ -1,3 +1,5 @@
+#see http://dateutil.readthedocs.io/en/stable/rrule.html
+
 reglement_piano:
   periodicity: monthly
   date-begin: -4