sorry first link must be http://www.freebsd.org/cgi/man.cgi?query=nl&apropos=0&sektion=1&manpath=FreeBSD+8.2-RELEASE&format=html in which we can see:
STANDARDS
The nl utility conforms to IEEE Std 1003.1-2001 (``POSIX.1'').
HISTORY
The nl utility first appeared in AT&T System V Release 2 UNIX.
