Add a reference to the material on string methods.
diff --git a/Doc/lib/libstring.tex b/Doc/lib/libstring.tex
index b04dbbe..6abcd13 100644
--- a/Doc/lib/libstring.tex
+++ b/Doc/lib/libstring.tex
@@ -53,8 +53,11 @@
is undefined.
\end{datadesc}
-The functions defined in this module are:
+Many of the functions provided by this module are also defined as
+methods of string and Unicode objects; see ``String Methods'' (section
+\ref{string-methods}) for more information on those.
+The functions defined in this module are:
\begin{funcdesc}{atof}{s}
Convert a string to a floating point number. The string must have