diff -r 6103b0eadbf2 -r f7c97e64cc2a ProgTutorial/document/root.bib
--- a/ProgTutorial/document/root.bib	Tue May 14 17:45:13 2019 +0200
+++ b/ProgTutorial/document/root.bib	Thu May 16 19:56:12 2019 +0200
@@ -9,6 +9,14 @@
                   delivered on 22nd January 2004 at the School of
                   Computing Science, Middlesex University}
 }
+@Misc{wenzel-technology,
+  author = {M.~Wenzel},
+  title = {Further Scaling of Isabelle Technology},
+  howpublished = {http://sketis.net},
+  month = {April},
+  year = {2018},
+  note = {},
+}
 
 @Book{isa-tutorial,
   author	= {T.~Nipkow and L.~C.~Paulson and M.~Wenzel},