Cordero, N., K. Cronin, G. Shishkin, L. Shishkina, and M. Stynes. “Finite Difference Scheme for a Singularly Perturbed Parabolic Equations in the Presence of Initial and Boundary Layers”. *Mathematical Modelling and Analysis*, vol. 13, no. 4, Dec. 2008, pp. 483-92, doi:10.3846/1392-6292.2008.13.483-492.