Burrington, Richard Stevens, Handbook of Mathematical Tables and Formulas,
Handbook Publishers, Inc., Sandusky, Ohio, 2nd edition, 1940, pp. 11-15, 20-21.
Beyer, William H., CRC Standard Mathematical Tables, CRC Press, Inc., Boca Raton,
Florida, 28th edition, 1987, pp. 121-132, 145-147.
Contributed by "Dr. Rob," Robert L. Ward
Web page design, diagrams, and applets by Sarah Seastone