--- a/slides/slides05.tex	Wed Oct 24 20:37:37 2018 +0100
+++ b/slides/slides05.tex	Thu Oct 25 00:50:58 2018 +0100
@@ -598,15 +598,17 @@
 A grammar for palindromes over the alphabet~\bl{$\{a,b\}$}:
 
 \bl{\begin{plstx}[margin=3cm]
-: \meta{S} ::= \epsilon\\
 : \meta{S} ::= a\cdot\meta{S}\cdot a\\
 : \meta{S} ::= b\cdot\meta{S}\cdot b\\
+: \meta{S} ::= a\\
+: \meta{S} ::= b\\
+: \meta{S} ::= \epsilon\\
 \end{plstx}}\pause
 
 or
 
 \bl{\begin{plstx}[margin=2cm]
-: \meta{S} ::=  \epsilon | a\cdot \meta{S}\cdot a | b\cdot \meta{S}\cdot b \\
+: \meta{S} ::=  a\cdot \meta{S}\cdot a | b\cdot \meta{S}\cdot b | a | b | \epsilon\\
 \end{plstx}}\pause\bigskip
 
 \small