FILASETA, Michael; SOLAN, Ikhalfani. An extension of a theorem by Ljunggren. Mathematica Scandinavica, Berkeley, CA, United States, v. 84, n. 1, p. 5–10, 1999. DOI: 10.7146/math.scand.a-13928. Disponível em: https://journals.msp.org/mscand/article/view/968. Acesso em: 25 jul. 2026.