--- a/Prefix_subtract.thy	Tue Mar 15 15:53:22 2011 +0000
+++ b/Prefix_subtract.thy	Wed Mar 23 12:17:30 2011 +0000
@@ -1,5 +1,6 @@
 theory Prefix_subtract
-  imports Main List_Prefix
+  imports Main 
+          "~~/src/HOL/Library/List_Prefix"
 begin
 
 section {* A small theory of prefix subtraction *}