CALDAS, Miguel; EKICI, Erdal; JAFARI, Saeid. On ?-closure spaces. Pro Mathematica, [S. l.], v. 20, n. 39-40, p. 119–133, 2006. Disponível em: https://revistas.pucp.edu.pe/index.php/promathematica/article/view/10242. Acesso em: 27 dic. 2025.