CONTRIBUTORS

--- a/CONTRIBUTORS	Thu May 30 23:29:33 2013 +0200
+++ b/CONTRIBUTORS	Fri May 31 07:30:23 2013 +0200
@@ -6,6 +6,9 @@
 Contributions to this Isabelle version
 --------------------------------------
 
+* May 2013: Lukas Bulwahn and Nicolai Schaffroth, TUM
+  HOL-Spec_Check: A Quickcheck tool for Isabelle's ML environment.
+
 * April 2013: Stefan Berghofer, secunet Security Networks AG
   Dmitriy Traytel, TUM
   Makarius Wenzel, Université Paris-Sud / LRI