K. Y. Sze, W. G. Jin, N. Sheng, and J. Li, “Trefftz methods for plane piezoelectricity”, Comp. Assist. Methods Eng. Sci., vol. 10, no. 4, pp. 619–627, Jan. 2023, Accessed: Jun. 30, 2025. [Online]. Available: https://cames.ippt.pan.pl/index.php/cames/article/view/1070