--- a/ProgTutorial/Tactical.thy	Wed Oct 26 12:59:44 2011 +0100
+++ b/ProgTutorial/Tactical.thy	Wed Oct 26 13:18:51 2011 +0100
@@ -14,9 +14,9 @@
 
 text {*
    \begin{flushright}
-  {\em ``The most effective debugging tool is still careful thought, coupled with 
-  judiciously placed print statements.''} \\[1ex]
-  Brian Kernighan 
+  {\em ``The most effective debugging tool is still careful thought,\\ 
+  coupled with judiciously placed print statements.''} \\[1ex]
+  Brian Kernighan, in {\em Unix for Beginners}, 1979
   \end{flushright}
 
   \medskip