Kompiš, Vladimír, and Mário Štiavnicky. “Trefftz Functions in FEM, BEM and Meshless Methods”. Computer Assisted Methods in Engineering and Science 13, no. 3 (September 30, 2006): 417–426. Accessed March 5, 2026. https://cames.ippt.gov.pl/index.php/cames/article/view/943.