Nguyen XT, Nguyen THP, Ong VT, Luong QT. ω-cover, k-cover and related spaces on the Pixley-Roy PR[X]. NSEN [Internet]. 2024 Dec. 14 [cited 2026 Sep. 10];14(5):60-6. Available from: https://dthujs.vn/index.php/nsen/article/view/2009