عدنان ظريف, سليمان محمود, and مروه شلاح. “Study of the Structure of Bitopological Spaces”. Tishreen University Journal -Basic Sciences Series, vol. 44, no. 2, June 2022, pp. 161-70, https://journal.tishreen.edu.sy/index.php/bassnc/article/view/12729.