mention cPickle and cStringIO
diff --git a/Doc/lib/libundoc.tex b/Doc/lib/libundoc.tex
index 4501a5b..368c6a4 100644
--- a/Doc/lib/libundoc.tex
+++ b/Doc/lib/libundoc.tex
@@ -10,6 +10,10 @@
 
 ni.py -- New import scheme with package support
 
+cPickle.c -- mostly the same as pickle but no subclassing
+
+cStringIO.c -- mostly the same as StringIO but no subclassing
+
 
 \section{Frameworks; somewhat harder to document, but
 well worth the effort}