🚀 go-pugleaf

After following up an earlier news item on nroff documentation, today I
received my copy of

	Nancy Dawson,
	UNIX Word Processing at HAO,
	(For Use with the 4.2 BSD Version and -me Macro Package),
	National Center for Atmospheric Research Technical Note
	NCAR/TN-263 + IA, January 1986.

It's a very well written and presented guide to troff'ing with
the -ms package.  Unfortunately we use the -mm package.  Now Dawson
refers to two publications which use the -ms package:

	Birns, Peter M, Patrick Brown, and John C C Muster,
	UNIX for People: a Modular Guide to the UNIX Operating System, Visual
	  Editing, Document Preparation, and Other Resources,
	Prentice-Hall, 1985; and

	Foster, Diana, and Kathryn Hemness (revised by Kelli Gant-Errek),
	ms Dictionary,
	UC Davis Computer Center, 1983.

My query is:  can anyone point me towards similar documents to help
new typists/word processors master n/t/ditroff using the -mm package?

(Incidentally, why three packages?  How do they substantively differ?)

Thanks in advance.