IBRAHIM, H. Z. Operation on Regular Spaces. Journal of Advanced Studies in Topology, [S. l.], v. 4, n. 1, p. 138:149, 2012. DOI: 10.20454/jast.2013.521. Disponível em: http://www.m-sciences.com/index.php/jast/article/view/521. Acesso em: 5 mar. 2021.