GOODSTEIN, R. L. Logic-free formalisations of recursive arithmetic. Mathematica Scandinavica, Berkeley, CA, United States, v. 2, p. 246–260, 1954. DOI: 10.7146/math.scand.a-10412. Disponível em: https://journals.msp.org/mscand/article/view/2910. Acesso em: 25 jul. 2026.