minor markup nits; fix missing whitespace

Doc/ref/ref2.tex

@@ -397,8 +397,8 @@ String literals are described by the following lexical definitions:
 One syntactic restriction not indicated by these productions is that
 whitespace is not allowed between the \grammartoken{stringprefix} and
 the rest of the string literal. The source character set is defined
-by the encoding declaration; it is \ASCII if no encoding declaration
-is given in the source file; see \ref{encodings}.
+by the encoding declaration; it is \ASCII{} if no encoding declaration
+is given in the source file; see section~\ref{encodings}.
 
 \index{triple-quoted string}
 \index{Unicode Consortium}