Let denote the number of zeros of in the
sector . If , , are real, , , , ,
, and, without loss of generality, ,
(compare (15.8.1)), then
If , , , , or , then
is not defined, or reduces to a polynomial, or
reduces to times a polynomial.
For further information on the location of real zeros see
Zarzo et al. (1995). A small table of zeros is given in
Conde and Kalla (1981) and Segura (2008).