MAJEED, R. N.; NASIR, A. I. Some Results on Semi-preopen Sets. Ibn AL-Haitham Journal For Pure and Applied Sciences, Baghdad, Iraq., v. 22, n. 3, 2017. Disponível em: https://jih.uobaghdad.edu.iq/index.php/j/article/view/1204. Acesso em: 14 mar. 2025.