This chapter is based in part on Chapter 15 of
Abramowitz and Stegun (1964) by Fritz Oberhettinger. The
author thanks Richard Askey and Simon Ruijsenaars for many helpful recommendations.
The main references used in writing this chapter are Andrews et al. (1999)
and Temme (1996b). For additional bibliographic reading see
Erdélyi et al. (1953a), Hochstadt (1971),
Luke (1969a), Olver (1997b), Slater (1966),
Wang and Guo (1989), and Whittaker and Watson (1927).