1. V. F. Butuzov, A. B. Vasil’eva, and N. N. Nefedov, “Asymptotic theory of contrasting structures: A survey,” Autom. Remote Control 58 (7), 1068–1091 (1997).
2. A. B. Vasil’eva, V. F. Butuzov, and N. N. Nefedov, “Contrasting structures in singularly perturbed problems,” Fundam Prikl. Mat. 4 (3), 799–851 (1998).
3. A. B. Vasil’eva, V. F. Butuzov, and N. N. Nefedov, “Singularly perturbed problems with boundary and internal layers,” Proc. Steklov Inst. Math. 268, 258–273 (2010).
4. A. B. Vasil’eva and V. F. Butuzov, Asymptotic Expansions of Solutions to Singularly Perturbed Equations (Nauka, Moscow, 1973) [in Russian].
5. N. Nefedov, “Comparison principle for reaction-diffusion-advection problems with boundary and internal layers,” Lect. Notes Comput. Sci. 823, 62–72 (2013).