Tam, Nguyễn Văn, Đào Văn Thành, and Phạm Thanh Giang. “The Security Internet Phone System”. <i>Journal of Computer Science and Cybernetics</i> 21, no. 4 (July 24, 2012): 312–322. Accessed April 6, 2026. https://cip.vast.vn/jcc/article/view/1435.