"Imperial Software Technology announced in conjunction
with O'Reilly & Associates, Inc. that Volumes 6A and 6B of the
'Definitive Guides to the X Window System' series of books are now
available for direct and free download in various formats and
Volume 6A is the Motif Programming Manual.
Volume 6B is the Motif Reference Manual.
The versions that can be downloaded from both the Imperial
Software Technology and Motifdeveloper.com web sites are later
versions than those made available by O'Reilly themselves. In
particular, Volume 6A from IST is for Motif 2.1, whereas from
O'Reilly it is for Motif 1.2."