MORDELL, L. J. Note on simultaneous quadratic congruences. Mathematica Scandinavica, Berkeley, CA, United States, v. 5, p. 21–26, 1957. DOI: 10.7146/math.scand.a-10485. Disponível em: https://journals.msp.org/mscand/article/view/2832. Acesso em: 8 sep. 2026.