GAVRYLKIV, V.M. Superextensions of three-element semigroups. Carpathian Mathematical Publications, [S. l.], v. 9, n. 1, p. 28–36, 2017. DOI: 10.15330/cmp.9.1.28-36. Disponível em: https://journals.pnu.edu.ua/index.php/cmp/article/view/1444. Acesso em: 1 may. 2024.