> https://www.tuhs.org/Archive/Documentation/Manuals/Unix_4.0/Volume_1/C.1.2_NROFF_TROFF_Users_Manual.pdf
Since PDF didn't exist in 1981, the document is either a scan or the result of a recent *roff run on ancient source. If it was made from source, it's an impressive testimonial to the longevity and stability of troff. Most probably it's a scan, in which case we owe many thanks to the public-spirited person who digitized this trove. Was it you, Arnold? Doug
