AUBERT, K. E. On the ideal theory of commutative semi-groups. MATHEMATICA SCANDINAVICA, [S. l.], v. 1, p. 39–54, 1953. DOI: 10.7146/math.scand.a-10363. Disponível em: https://www.mscand.dk/article/view/10363. Acesso em: 2 may. 2024.