diff -r ce53d799ee64 -r a6f2847465eb Cookbook/index.html
--- a/Cookbook/index.html	Fri Jun 16 21:49:32 2017 +0100
+++ b/Cookbook/index.html	Tue Jul 18 17:19:31 2017 +0100
@@ -5,7 +5,7 @@
     <meta content="text/html; charset=ISO-8859-1" http-equiv="content-type">
     <title>Isabelle Programming Tutorial</title>
     <link rel="stylesheet" href="nominal.css">
-    <BASE HREF="http://nms.kcl.ac.uk/christian.urban/">
+    <BASE HREF="https://nms.kcl.ac.uk/christian.urban/">
     <script type="text/javascript">
 
   var _gaq = _gaq || [];