Cordero, Nicolas, Kevin Cronin, Grigorii Shishkin, Lida Shishkina, and Martin Stynes. “Finite Difference Scheme for a Singularly Perturbed Parabolic Equations in the Presence of Initial and Boundary Layers”. Mathematical Modelling and Analysis 13, no. 4 (December 31, 2008): 483-492. Accessed December 12, 2019. https://journals.vgtu.lt/index.php/MMA/article/view/7035.