kadham Al-talkany, Yiezi, Ameer A.J. AL-Swidi, and Ali Younis Shaker. “Topological Study via σ-Algebra”. Journal of Al-Qadisiyah for computer science and mathematics 8, no. 1 (August 9, 2017): 78-82. Accessed August 30, 2021. http://www.qu.edu.iq/journalcm/index.php/journalcm/article/view/46.