1. V. T. Volkov and N. N. Nefedov, “Development of the Asymptotic Method of Differential Inequalities for Investigation of Periodic Contrast Structures in Reaction-Diffusion Equations,” Zh. Vychisl. Mat. Mat. Fiz. 46(4), 615–623 (2006) [Comput. Math. Math. Phys. 46 (4), 585–593 (2006)].
2. A. B. Vasil’eva and V. F. Butuzov, Asymptotic Methods in the Theory of Singular Perturbations (Vyssh. Shkola, Moscow, 1990) [in Russian].
3. N. N. Nefedov, “An Asymptotic Method for Differential Inequalities in the Investigation of Periodic Contrast Structures: Existence, Asymptotics and Stability,” Differ. Uravn. 36(2), 262–269 (2000) [Differ. Equ. 36 (2), 298–305 (2000)].
4. N. N. Nefedov, “The Method of Differential Inequalities for Some Classes of Nonlinear Singularly Perturbed Problems with Internal Layers,” Differ. Uravn. 31 (7), 1142–1149 (1995) [Differ. Equ. 31 (7), 1077–1085 (1995)].
5. N. Nefedov, “Comparison Principle for Reaction-Diffusion-Advection Problems with Boundary and Internal Layers,” Lecture Notes in Comput. Sci. 8236, 62–72 (2013).