J. A. T. de Freitas, “Time integration and the Trefftz Method Part I - First-order and parabolic problems”, CAMES, vol. 10, no. 4, pp. 453–463, Jan. 2023, Accessed: Jan. 12, 2025. [Online]. Available: https://cames3.ippt.pan.pl/index.php/cames/article/view/1057