Daniel K. Schneider, TECFA, University of Geneva
http://tecfa.unige.ch/guides/xml/frame-sgml/
Should be usable somewhat., but it certainly is rough draft quality
This is a very short guide to help you editing structured documents with FrameMaker + SGML (version 6). It is meant for a "tech savy" audience. In addition you should skim through the FrameMaker+SGML book you get with the software and which is well done but too verbose. Note, that there are also companion documents for somewhat XML savy users who want to work with their own structure definitions, see:
http://tecfa.unige.ch/guides/xml/frame-sgml/