Hi,
A scan of the printed UNIX Version 6 documents set is now online
at the link below since last week. The set consists of documents
accompanying the manual pages in the programmer's manual (similar
to volume 2 in v7).
https://www.computerhistory.org/collections/catalog/102659317
The [nt]roff user manual, tmg compiler-compiler, and m6 macro
processor memos were previously missing from the distributions
in TUHS and later efforts to re-create the documentation.
I have been working on finding this documentation as part of
researching roff history. Still interested in earlier copies of
the internal memoranda from Ossanna that served as the NROFF
User's Manual since v3, the TROFF User's Manual after v5, and
TROFF Made Trivial starting around v4. Based on the manpage
histories, the documentation was revised for v4, 5, and 6.
Best,
Dan Plassche