Nguyen Thi Thu, Nguyen Hoang Duong, and Pham Quang Minh. “RESEARCH ON THE FREE BULGING STAGE IN HYDROSTATIC FORMING PROCESS FOR COPPER SHEET”. UTEHY Journal of Science and Technology, Vol. 33, Mar. 2022, pp. 87-92, http://jst.utehy.edu.vn/index.php/jst/article/view/527.