WILLIAMS, K. S. 3 as a Ninth Power (mod $p$). MATHEMATICA SCANDINAVICA, [S. l.], v. 35, p. 309–317, 1974. DOI: 10.7146/math.scand.a-11555. Disponível em: https://www.mscand.dk/article/view/11555. Acesso em: 29 mar. 2024.