ASKEY, R.; HIRSCHMAN, I. I. J. Mean Summability for Ultraspherical Polynomials. MATHEMATICA SCANDINAVICA, [S. l.], v. 12, p. 167–177, 1963. DOI: 10.7146/math.scand.a-10680. Disponível em: https://www.mscand.dk/article/view/10680. Acesso em: 26 apr. 2024.