The Closed Subsemigroups of a Clifford Semigroup. Communications in Mathematical Research, [S. l.], v. 30, n. 2, p. 97–105, 2021. DOI: 10.13447/j.1674-5647.2014.02.01. Disponível em: https://global-sci.com/index.php/cmr/article/view/8801. Acesso em: 5 dec. 2025.