diff -r 0baae4311a9f -r b9556a055632 src/HOL/Library/Countable_Set.thy
--- a/src/HOL/Library/Countable_Set.thy	Sun Nov 02 17:16:01 2014 +0100
+++ b/src/HOL/Library/Countable_Set.thy	Sun Nov 02 17:20:45 2014 +0100
@@ -3,7 +3,7 @@
     Author:     Andrei Popescu
 *)
 
-header {* Countable sets *}
+section {* Countable sets *}
 
 theory Countable_Set
 imports Countable Infinite_Set