FABRICIUS-BJERRE, Fr. On a conjecture of G. Bol. Mathematica Scandinavica, Berkeley, CA, United States, v. 40, p. 194–196, 1977. DOI: 10.7146/math.scand.a-11688. Disponível em: https://journals.msp.org/mscand/article/view/1958. Acesso em: 25 jul. 2026.