K. Banaś and M. F. Wheeler, “Preconditioning GMRES for discontinuous Galerkin approximations”, Comp. Assist. Methods Eng. Sci., vol. 11, no. 1, pp. 47–62, Jan. 2023, Accessed: Jun. 29, 2025. [Online]. Available: https://cames.ippt.pan.pl/index.php/cames/article/view/1043