Abramowitz and Stegun
Abramowitz and Stegun is the informal moniker of a mathematical reference work edited by Milton Abramowitz and Irene Stegun of the U.S. National Bureau of Standards. Its full title is Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables.
When it was first published in 1964, the 1000+ page Handbook was one of the most comprehensive sources of information on special functions, containing definitions, identities, approximations, plots, and tables of values of numerous functions used in virtually all fields of applied mathematics.
At the time of its publication, the Handbook was an essential resource for practitioners. Nowadays, computer algebra systems have replaced the function tables, but the Handbook remains an important reference source.
Because the Handbook is the product of US Government employees acting in official capacity, it is not protected by copyright. While it can be ordered from the Government Printing Office, it has also been reprinted by commerical publishers, most notably Dover Publications (ISBN 0486612724), and can be legally viewed and downloaded off the web (see below for URLs).
BibTeX entry:
@Book{abramowitz+stegun,
author = "Milton Abramowitz and Irene A. Stegun",
title = "Handbook of Mathematical Functions with
Formulas, Graphs, and Mathematical Tables",
publisher = "Dover",
year = 1964,
address = "New York",
edition = "ninth Dover printing, tenth GPO printing",
isbn = "0-486-61272-4"
}