diff -r 2457bea123e4 -r b73d8ed73b35 src/Pure/General/json.scala
--- a/src/Pure/General/json.scala	Sun Mar 11 15:05:43 2018 +0100
+++ b/src/Pure/General/json.scala	Sun Mar 11 15:06:48 2018 +0100
@@ -1,7 +1,7 @@
 /*  Title:      Pure/General/json.scala
     Author:     Makarius
 
-Support for JSON.
+Support for JSON: https://www.json.org/.
 */
 
 package isabelle