Kheunkhieo, P., and K. Tangchaichit. “3-Dimensional stress analysis of a ball swaging process using the finite element method”. Asia-Pacific Journal of Science and Technology, vol. 15, no. 7, Apr. 2017, pp. 581-9, https://so01.tci-thaijo.org/index.php/APST/article/view/83246.