diff -r 72d19e588e97 -r 90a3016a6c12 src/HOL/Data_Structures/Tree23_Set.thy
--- a/src/HOL/Data_Structures/Tree23_Set.thy	Mon Jan 11 18:27:27 2016 +0100
+++ b/src/HOL/Data_Structures/Tree23_Set.thy	Mon Jan 11 20:51:13 2016 +0100
@@ -1,6 +1,6 @@
 (* Author: Tobias Nipkow *)
 
-section \<open>A 2-3 Tree Implementation of Sets\<close>
+section \<open>2-3 Tree Implementation of Sets\<close>
 
 theory Tree23_Set
 imports