Added ref to StringIO docs.
diff --git a/Doc/lib/libstrings.tex b/Doc/lib/libstrings.tex
index ea9a099..ec4834b 100644
--- a/Doc/lib/libstrings.tex
+++ b/Doc/lib/libstrings.tex
@@ -17,4 +17,7 @@
\item[struct]
--- Interpret strings as packed binary data.
+\item[StringIO]
+--- Read and write strings as if they were files.
+
\end{description}
diff --git a/Doc/libstrings.tex b/Doc/libstrings.tex
index ea9a099..ec4834b 100644
--- a/Doc/libstrings.tex
+++ b/Doc/libstrings.tex
@@ -17,4 +17,7 @@
\item[struct]
--- Interpret strings as packed binary data.
+\item[StringIO]
+--- Read and write strings as if they were files.
+
\end{description}