[TUHS] Early supported UNIX manual

[Phil Budne]

> https://bitsavers.org/pdf/att/unix/6th_Edition/

When I showed my copy of the manual to Dennis Ritchie at a Usenix, and
asked him to identify it (and autograph it), he described it as "very
early supported UNIX".

I think of "Nth Edition" or "Version N" as releases (of the manual)
from the "research" group, and this manual is for something _close_ to
6th Edition, but it's not, in the strict sense, v6.

Not that I can tell you an easy name for what to call it!