diff -r 78bedf3026a2 -r 31536371dfdf index.html
--- a/index.html	Tue Jun 11 10:26:29 2019 +0100
+++ b/index.html	Tue Jun 11 10:27:43 2019 +0100
@@ -98,7 +98,7 @@
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   <IMG SRC="new.gif" ALT="" style="" align="left"><A HREF="https://nms.kcl.ac.uk/christian.urban/Cookbook" target="_top">Isabelle Programming Tutorial</A> (draft of a 200-page tutorial on Isabelle programming - updated to
-    Isabelle 2019 thanks to Norbert Schirmer)<BR><BR>
+    <A HREF="http://isabelle.in.tum.de">Isabelle 2019</A> thanks to Norbert Schirmer)<BR><BR>
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 </TR>