GREENBERG, Leon. Discrete Subgroups of the Lorentz Group. Mathematica Scandinavica, Berkeley, CA, United States, v. 10, p. 85–107, 1962. DOI: 10.7146/math.scand.a-10515. Disponível em: https://journals.msp.org/mscand/article/view/2672. Acesso em: 8 sep. 2026.