Nicola, Aurelian, and Constantin Popa. “Preconditioning by an Extended Matrix Technique for Convection-Diffusion-Reaction Equations”. Rev. Anal. Numér. Théor. Approx., vol. 37, no. 2, Aug. 2008, pp. 181-90, https://doi.org/10.33993/jnaat372-890.