diff --git a/scripts-available/CDB_GreatCircle.sql b/scripts-available/CDB_GreatCircle.sql
index 004ae2e..8d98dbf 100644
--- a/scripts-available/CDB_GreatCircle.sql
+++ b/scripts-available/CDB_GreatCircle.sql
@@ -1,3 +1,6 @@
+-- Great circle point-to-point routes, based on:
+--   http://blog.cartodb.com/jets-and-datelines/
+--
 CREATE OR REPLACE FUNCTION CDB_GreatCircle(start_point geometry, end_point geometry)
 RETURNS geometry AS $$
 DECLARE