--- a/slides/slides02.tex	Mon Oct 01 14:11:34 2018 +0100
+++ b/slides/slides02.tex	Mon Oct 01 14:21:37 2018 +0100
@@ -120,7 +120,9 @@
 \item \bl{$(a + a^?)^*$}
 \end{itemize}
 
-\item sometimes also called \alert{catastrophic backtracking}
+\item sometimes also called \alert{catastrophic backtracking}\bigskip
+\item \small\ldots I hope you have watched the video by the
+  StackExchange engineer  
 \end{itemize}
 
 \end{frame}