1. Fonctions Hypergéometriques et Hypersphériques, Polynomes d'Hermite;Appell,1926
2. Orthogonal polynomials and special functions;Askey,1975
3. Polynomial sequences of integral type;Barnabei;J. Math. Anal. Appl.,1980
4. Recursive methods and the umbral calculus;Barnabei;J. Algebra,1982
5. N. Bourbaki, “Fonctions d'une Réele Variable.”