Where rfc822.Message is mentioned, add a link to the rfc822 module.
diff --git a/Doc/lib/libmailbox.tex b/Doc/lib/libmailbox.tex
index 97c80e9..8beab4c 100644
--- a/Doc/lib/libmailbox.tex
+++ b/Doc/lib/libmailbox.tex
@@ -44,9 +44,10 @@
method:
\begin{methoddesc}[mailbox]{next}{}
-Return the next message in the mailbox, as a \class{rfc822.Message} object.
-Depending on the mailbox implementation the \var{fp} attribute of this
-object may be a true file object or a class instance simulating a file object,
-taking care of things like message boundaries if multiple mail messages are
+Return the next message in the mailbox, as a \class{rfc822.Message}
+object (see the \refmodule{rfc822} module). Depending on the mailbox
+implementation the \var{fp} attribute of this object may be a true
+file object or a class instance simulating a file object, taking care
+of things like message boundaries if multiple mail messages are
contained in a single file, etc.
\end{methoddesc}