JONES, Gareth A. Counting subgroups of non-euclidean crystallographic groups. Mathematica Scandinavica, Berkeley, CA, United States, v. 84, n. 1, p. 23–39, 1999. DOI: 10.7146/math.scand.a-13930. Disponível em: https://journals.msp.org/mscand/article/view/966. Acesso em: 24 jul. 2026.