diff -r 88dd06301dd3 -r 1f7308050349 src/HOL/Predicate_Compile_Examples/Reg_Exp_Example.thy
--- a/src/HOL/Predicate_Compile_Examples/Reg_Exp_Example.thy	Sat May 19 20:42:34 2018 +0200
+++ b/src/HOL/Predicate_Compile_Examples/Reg_Exp_Example.thy	Sun May 20 11:57:17 2018 +0200
@@ -4,7 +4,7 @@
   "HOL-Library.Code_Prolog"
 begin
 
-text \<open>An example from the experiments from SmallCheck (\<^url>\<open>http://www.cs.york.ac.uk/fp/smallcheck\<close>)\<close>
+text \<open>An example from the experiments from SmallCheck (\<^url>\<open>https://www.cs.york.ac.uk/fp/smallcheck\<close>)\<close>
 text \<open>The example (original in Haskell) was imported with Haskabelle and
   manually slightly adapted.
 \<close>