diff -r 4a5876f321ae -r b93f4d2aeee1 slides/slides04.tex
--- a/slides/slides04.tex	Sat Oct 15 14:27:01 2016 +0100
+++ b/slides/slides04.tex	Mon Oct 17 13:18:34 2016 +0100
@@ -936,13 +936,13 @@
   \bl{$(\ZERO \cdot (b \cdot c)) + ((\ZERO \cdot c) + \ONE)$}
   \end{center}
 
-  and answer
+  and answer how this regular expression matches the empty string
 
   \begin{center}
   \bl{$Right(Right(Empty))$}
   \end{center}\bigskip
 
-  But now we simplify to \bl{$\ONE$} and produce \bl{$Empty$}.
+  But now we simplify this to \bl{$\ONE$} and would produce \bl{$Empty$}.
 
 \end{frame}
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