TRUNG, P. Q. Some problems for an anular cover and relation concepts. Journal of Computer Science and Cybernetics, [S. l.], v. 17, n. 2, p. 65–74, 2012. DOI: 10.15625/1813-9663/17/2/2446. Disponível em: https://vjs.ac.vn/index.php/jcc/article/view/2446. Acesso em: 8 may. 2024.