Brink U, Kreienmeyer M, Peters K, Stein E. Aspects of Trefftz’ Method in BEM and FEM and their coupling. Comp. Assist. Methods Eng. Sci. 2023;4(3-4):327-344. Accessed June 30, 2025. https://cames.ippt.pan.pl/index.php/cames/article/view/1553