1. Introduction to Singular Perturbations;O'Malley,1974
2. Boundary-Layer Theory;Schlichting,1979
3. An elliptic interface problem: a review;Srivastava;Appl. Math. Inf. Sci. Lett.,2019
4. An integral solution for the diffusion-advection equation;Taigbenu;Water Resour. Res.,1986
5. Robust Numerical Methods for Singularly Perturbed Differential Equations;Roos,2008