SKOLEM, Th. Some Remarks on the Triple Systems of Steiner. Mathematica Scandinavica, Berkeley, CA, United States, v. 6, p. 273–280, 1958. DOI: 10.7146/math.scand.a-10551. Disponível em: https://journals.msp.org/mscand/article/view/2792. Acesso em: 25 jul. 2026.