Qin, Qing-Hua, and Ke-Yong Wang. “Application of Hybrid-Trefftz Finite Element Method to Frictional Contact Problems”. Computer Assisted Methods in Engineering and Science 15, no. 3-4 (December 31, 2008): 319–336. Accessed March 5, 2026. https://cames.ippt.gov.pl/index.php/cames/article/view/739.