SKOLEM, T. A Set Theory Based on a Certain 3-Valued Logic. MATHEMATICA SCANDINAVICA, [S. l.], v. 8, p. 127–136, 1960. DOI: 10.7146/math.scand.a-10600. Disponível em: https://www.mscand.dk/article/view/10600. Acesso em: 14 apr. 2025.