http://wks.uts.ohio-state.edu/unix_course/intro-135.html — Emacs Quick Reference Guide

Emacs reference card that comes with the emacs package. You can print it out as a reference. — /usr/share/emacs/version/etc/refcard.ps

Read Editing XML with Emacs and PSGML in /usr/share/doc/psgml-version/psgml.ps.

http://www.snee.com/bob/sgmlfree/psgmqref.html — Emacs/PSGML Quick Reference is a reference table of Emacs commands for PSGML mode.

http://www.snee.com/bob/sgmlfree/emcspsgm.html — PSGML Tricks