GRIFFIN, M. P. The Pythagorean closure of fields. MATHEMATICA SCANDINAVICA, [S. l.], v. 38, p. 177–191, 1976. DOI: 10.7146/math.scand.a-11627. Disponível em: https://www.mscand.dk/article/view/11627. Acesso em: 9 may. 2024.