Integrals and integral equations for ${\mathrm{𝖯𝗌}}_n^m(x,{\gamma }^2)$ are given in Arscott (1964b, §8.6), Erdélyi et al. (1955, §16.13), Flammer (1957, Chapter 5), and Meixner (1951). For product formulas and convolutions see Connett et al. (1993). For an addition theorem, see Meixner and Schäfke (1954, p. 300) and King and Van Buren (1973). For expansions in products of spherical Bessel functions, see Flammer (1957, Chapter 6).