1. L. Gegenbauer, Zur Theorie der Functionen 𝐶_{𝑛}^{𝑣}(𝑥), Denkschriften der Akademie der Wissenschaften in Wien, Math. Naturwiss. Kl. 48 (1884), 293-316.
2. Harmonic Analysis of Functions of Several
Complex Variables in the Classical Domains
3. G. Szegö, Orthogonal polynomials, rev. ed., Amer. Math. Soc. Colloq. Publ. Vol. 23, Amer. Math. Soc., Providence, R. I., 1959.