Lions Book n.
"Source Code and Commentary on Unix level 6", by John Lions.
The two parts of this book contained (1) the entire source
listing of the Unix Version 6 kernel, and (2) a commentary on the
source discussing the algorithms. These were circulated
internally at the University of New South Wales beginning
1976-77, and were, for years after, the only detailed
kernel documentation available to anyone outside Bell Labs.
Because Western Electric wished to maintain trade secret status
on the kernel, the Lions Book was only supposed to be distributed
to affiliates of source licensees. In spite of this, it soon
spread by samizdat to a good many
of the early Unix hackers.
[1996 update: The Lions book lives again! It was put back in
print as ISBN 1-57398-013-7 from Peer-To-Peer Communications,
with forewords by Dennis Ritchie and Ken Thompson. In a neat bit
of reflexivity, the page before the contents quotes this
entry.]