--- a/topics.tex	Sun Nov 11 17:28:11 2012 +0000
+++ b/topics.tex	Wed Nov 14 00:02:38 2012 +0000
@@ -17,19 +17,20 @@
 
 \begin{itemize}
 \item What is a language?
-\item concatenation of two sets of string
+\item concatenation of two sets of strings
 \item power of a set of strings
 \end{itemize}
 
 \section{Regular Expressions}
 
 \begin{itemize}
+\item definition of regular expressions
 \item What is the language of a regular expression?
 \item When are two regular expressions are equal?
 \item {\it nullable}, {\it der}, {\it zeroable}, {\it rev}
 \item induction principle of regular expressions
 \item tokens, maximal munch rule
-\item ``negative'' regular expression 
+\item regular expression for complement language 
 \item tokenisation
 \end{itemize}