1.1 --- a/src/HOL/ex/BT.thy	Sun Nov 02 18:21:14 2014 +0100
     1.2 +++ b/src/HOL/ex/BT.thy	Sun Nov 02 18:21:45 2014 +0100
     1.3 @@ -5,7 +5,7 @@
     1.4  Binary trees
     1.5  *)
     1.6  
     1.7 -header {* Binary trees *}
     1.8 +section {* Binary trees *}
     1.9  
    1.10  theory BT imports Main begin
    1.11