GREENBERG, L. Discrete Subgroups of the Lorentz Group. MATHEMATICA SCANDINAVICA, [S. l.], v. 10, p. 85–107, 1962. DOI: 10.7146/math.scand.a-10515. Disponível em: https://www.mscand.dk/article/view/10515. Acesso em: 23 jul. 2024.