diff --git a/point_downloader.js b/point_downloader.js
index cfdf49c..6289301 100644
--- a/point_downloader.js
+++ b/point_downloader.js
@@ -1,3 +1,8 @@
+/*
+ Most of the code here is straight out of Google's example code at
+ https://developers.google.com/maps/documentation/javascript/examples/marker-remove
+*/
+
 var map;
 var markers = [];