Abramowitz and Stegun 1964
M. Abramowitz and I. A. Stegun, Handbook of Mathematical Functions, Dover, 1046 pp. 1964.
A very important book, containing a number of chapters written by various authors. Most of the book is devoted to numerical tables which have long since become redundant but it contains a wealth of material. It was very important for establishing the notation for Bessel functions etc. There have been a number of additions.
The 10th edition (1972) is available online (as a scan of the book).