Added link to Fredrik Lundh's online Tkinter reference material.
diff --git a/Doc/lib/libundoc.tex b/Doc/lib/libundoc.tex
index 657589b..cfa8445 100644
--- a/Doc/lib/libundoc.tex
+++ b/Doc/lib/libundoc.tex
@@ -15,7 +15,10 @@
\begin{description}
\item[Tkinter.py]
--- Interface to Tcl/Tk for graphical user interfaces;
-Fredrik Lundh is working on this one!
+Fredrik Lundh is working on this one! See \emph{An Introduction to
+Tkinter} at
+\url{http://www.pythonware.com/library/tkinter/introduction} for
+on-line reference material.
\item[Tkdnd.py]
--- Drag-and-drop support for \module{Tkinter}.