E. Stein and S. Ohnimus, “Equilibrium method for postprocessing and error estimation in the finite element method”, CAMES, vol. 4, no. 3-4, pp. 645–666, Jun. 2023, Accessed: Jan. 12, 2025. [Online]. Available: https://cames3.ippt.pan.pl/index.php/cames/article/view/1396