fix to C0

book.tex

@@ -1717,7 +1717,7 @@ C_0 & ::= & (\itm{label}\key{:}~ \Tail)^{+}
 \Atm &::=& \INT{\Int} \mid \VAR{\Var} \\
 \Exp &::=& \Atm \mid \READ{} \mid \NEG{\Atm} \\
  &\mid& \ADD{\Atm}{\Atm}\\
-\Stmt &::=& \ASSIGN{\Var}{\Exp} \\
+\Stmt &::=& \ASSIGN{\VAR{\Var}}{\Exp} \\
 \Tail &::= & \RETURN{\Exp} \mid \SEQ{\Stmt}{\Tail} \\
 C_0 & ::= & \PROGRAM{\itm{info}}{\CFG{\key{(}\itm{label}\,\key{.}\,\Tail\key{)}^{+}}}
 \end{array}