1. E. P. Doolan, J. Miller, and W. S. Childers, Uniform Numerical Methods for Problems with Initial and Boundary Layers, Boole Press, Dublin (1980).
2. N. S. Bakhvalov,“Optimization of methods of solution of boundary-value problems in the presence of a boundary layer,” Zh. Vychisl. Mat. Mat. Fiz.,9, No. 4, 841–859 (1969).
3. Yu. P. Boglayev,“Numerical methods of solution of singularly perturbed problems,” Diff. Uravn..21, No. 10, 1804–1806 (1985).
4. A. H. Nayfeh, Perturbation Methods [Russian translation], Mir, Moscow (1976).
5. A. B. Vasil’eva and V. F. Butuzov, Asymptotic Expansions of Solutions of Singularly Perturbed Equations [in Russian], Nauka, Moscow (1973).