typo

book.tex

@@ -692,9 +692,8 @@ necessary for integers.) In Figure~\ref{fig:pe-arith}, the normal
 structural recursion is captured in the main \texttt{pe-arith}
 function whereas the code for partially evaluating negation and
 addition is factored out the into two separate helper functions:
-\texttt{pe-neg} and \texttt{pe-add}. Note that the inputs two these
-helper functions is the output of partially evaluating the children
-nodes.
+\texttt{pe-neg} and \texttt{pe-add}. The input to these helper
+functions is the output of partially evaluating the children nodes.
 
 \begin{figure}[tbp]
 \begin{lstlisting}