MD TAP, Abu Osman; ABDULLAH, Izzah; SALLEH, Abd. Razak. Set Semiterbuka dan Semitertutup Kabur. MATEMATIKA, [S. l.], v. 8, p. 125–131, 1992. DOI: 10.11113/matematika.v8.n.466. Disponível em: https://matematika.utm.my/index.php/matematika/article/view/466. Acesso em: 3 may. 2024.