PWB Unix was the earliest sources I could find. FreeBSD lists history items for releases going back to the earliest unix release because BSD Unix is derived fro

PWB Unix was the earliest sources I could find. FreeBSD lists history items for releases going back to the earliest unix release because BSD Unix is derived from AT&T Research Unix and FreeBSD is derived from 4.4BSD... The tabs file does predate this, and I'll make a note of that (which is what this article is about).