Huy, Nguyễn Xuân, Lê Đức Minh, and Vũ Ngọc Loãn. “Closed Mappings and Application in Databases”. Journal of Computer Science and Cybernetics 16, no. 4 (April 15, 2013): 1–6. Accessed November 5, 2025. https://jcc.vast.vn/jcc/article/view/2914.