--- a/doc-src/TutorialI/CTL/CTL.thy Wed Oct 11 13:33:38 2000 +0200
+++ b/doc-src/TutorialI/CTL/CTL.thy Wed Oct 11 13:39:52 2000 +0200
@@ -386,7 +386,7 @@
%{text[display]"| EU formula formula E[_ U _]"}
%which enables you to read and write {text"E[f U g]"} instead of {term"EU f g"}.
\end{exercise}
-For more CTL exercises see, for example \cite{Huth-Ryan-book,Clarke-as-well?}.
+For more CTL exercises see, for example \cite{Huth-Ryan-book}.
\bigskip
Let us close this section with a few words about the executability of our model checkers.