C.-Y. Lee, Q.-H. Qin, and H. Wang, “Trefftz functions and application to 3D elasticity”, CAMES, vol. 15, no. 3-4, pp. 251–263, Jul. 2022, Accessed: Jan. 12, 2025. [Online]. Available: https://cames3.ippt.pan.pl/index.php/cames/article/view/734