--- a/src/HOL/BNF/Examples/Derivation_Trees/DTree.thy Mon Dec 02 20:31:54 2013 +0100
+++ b/src/HOL/BNF/Examples/Derivation_Trees/DTree.thy Mon Dec 02 20:31:54 2013 +0100
@@ -11,8 +11,6 @@
imports Prelim
begin
-hide_fact (open) Lifting_Product.prod_rel_def
-
typedecl N
typedecl T