AL-SALAM, W. A. On the product of two Legendre polynomials. Mathematica Scandinavica, Berkeley, CA, United States, v. 4, p. 239–242, 1956. DOI: 10.7146/math.scand.a-10471. Disponível em: https://journals.msp.org/mscand/article/view/2852. Acesso em: 8 sep. 2026.