4.2bsd: Where does it say that orphan processes die when they stop?

[idallen at watmath.UUCP]

Can someone tell me where the following Berkeley 4.2 behaviour is
documented (other than the kernel source, that is):

1) When a process exits the kernel sends SIGHUP and then SIGCONT to
   all its children that are stopped with SIGTSTP, SIGTTIN, or SIGTTOU.

2) If an orphan process (one whose parent has exited, resulting in the
   process having INIT as a parent) receives SIGTSTP, SIGTTIN, or
   SIGTTOU, and tries to stop, the kernel will SIGKILL it dead.

How long has this behaviour been in there?  4.1bsd?  Earlier?
The latter behaviour is what makes this CSH output disappear:

   % stty -tostop ; (date&) ; stty tostop ; (date&)
-- 
        -IAN!  (Ian! D. Allen)      University of Waterloo