Aziz Hussain Al-Abdulla, Raad, and Sema Kadhim Gaber. “bopen Sets In Topological Spaces”. Journal of Al-Qadisiyah for Computer Science and Mathematics, vol. 2, no. 2, Sept. 2017, pp. 77-88, https://jqcsm.qu.edu.iq/index.php/journalcm/article/view/225.