README

--- a/README	Wed Jul 18 12:21:55 2018 +0200
+++ b/README	Wed Jul 18 16:44:01 2018 +0200
@@ -34,10 +34,10 @@
    The Isabelle home page may be accessed from the following mirror
    sites:
 
-     * http://www.cl.cam.ac.uk/research/hvg/Isabelle
-     * http://isabelle.in.tum.de
+     * https://www.cl.cam.ac.uk/research/hvg/Isabelle
+     * https://isabelle.in.tum.de
      * http://mirror.cse.unsw.edu.au/pub/isabelle
-     * http://mirror.clarkson.edu/isabelle
+     * https://mirror.clarkson.edu/isabelle
 
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