SKOLEM, Th. Some considerations concerning recursive functions. Mathematica Scandinavica, Berkeley, CA, United States, v. 1, p. 213–221, 1953. DOI: 10.7146/math.scand.a-10379. Disponível em: https://journals.msp.org/mscand/article/view/2943. Acesso em: 25 jul. 2026.