--- a/src/HOL/UNITY/Comp/Counter.thy	Wed May 25 11:49:40 2016 +0200
+++ b/src/HOL/UNITY/Comp/Counter.thy	Wed May 25 11:50:58 2016 +0200
@@ -8,7 +8,7 @@
    Springer LNCS 1586 (1999), pages 1215-1227.
 *)
 
-section{*A Family of Similar Counters: Original Version*}
+section\<open>A Family of Similar Counters: Original Version\<close>
 
 theory Counter imports "../UNITY_Main" begin