kadham Al-talkany Y, A.J. AL-Swidi A, Younis Shaker A. Topological study via σ-algebra. JQCM [Internet]. 9Aug.2017 [cited 30Aug.2021];8(1):78-2. Available from: http://www.qu.edu.iq/journalcm/index.php/journalcm/article/view/46