+.SH CONFORMING TO
That should be ".SH STANDARDS".
We use CONFORMING TO in Linux. Don't know why; just history, I guess.
See man-pages(7).
Weird.
I failed to find a single instance of "CONFORMING TO" in AT&T UNIX
(including v6, PWB, v7, 32v, v8, v10, System III, SVR1, SVR2) nor in
any version of UCB CSRG BSD. So considering that System V and BSD are
widely considered the two main original branches of the development
of Unix-like operating systems and Linux is often considered to have
drawn inspiration from both, the section name "CONFORMING TO" does
not appear to be a UNIX thing. For example, Aeleen Frisch, "Essential
System Administration", O'Reilly, Cambridge 1995, considers Linux
as slightly more influenced by 4.3BSD than by System V Release 3.
STANDARDS, on the other hand, is present since 4.3BSD-Reno (June 1990).
4.3BSD-Reno predates the first version of the Linux kernel by more than
a year, and the first Linux manual pages probably for longer than that.
So i have no idea where "CONFORMING TO" may have come from.