MD TAP, Abu Osman. Pencirian Beberapa Set Hampir Terbuka dan Set Hampir Tertutup. MATEMATIKA, [S. l.], v. 10, p. 7–8, 1994. DOI: 10.11113/matematika.v10.n.49. Disponível em: https://matematika.utm.my/index.php/matematika/article/view/49. Acesso em: 20 may. 2024.