fixes from trajafri

book.tex

@@ -1773,7 +1773,7 @@ statements always ends with \key{Return}, a guarantee that is baked
 into the grammar rules for the \itm{tail} non-terminal. The naming of
 this non-terminal comes from the term \emph{tail position}\index{tail position},
 which refers to an expression that is the last one to execute within a
-function. (A expression in tail position may contain subexpressions,
+function. (An expression in tail position may contain subexpressions,
 and those may or may not be in tail position depending on the kind of
 expression.)
 
@@ -2008,7 +2008,7 @@ R^{\dagger}_1  &::=& \PROGRAM{\code{'()}}{\Exp}
 Figure~\ref{fig:r1-anf-syntax} presents the grammar for the output of
 this pass, language $R_1^{\dagger}$. The main difference is that
 operator arguments are required to be atomic expressions.  In the
-literature this is called \emph{administrative normal form}, or ANF
+literature, this is called \emph{administrative normal form}, or ANF
 for short~\citep{Danvy:1991fk,Flanagan:1993cg}.
 \index{administrative normal form}
 \index{ANF}