1. Ainsworth, M., Babuška, I.: Reliable and robust a posteriori error estimating for singularly perturbed reaction-diffusion problems. SIAM J. Numer. Anal., 36, 331–353 (1999)
2. Apel, T.: Anisotropic Finite Elements: Local Estimates and Applications. Teubner, Stuttgart (1999)
3. Babuška, I., Strouboulis, T.: The Finite Element Method and its Reliability. Clarendon Press, Oxford University Press, New York (2001)
4. Bakhvalov, N.S.: Towards optimization of methods for solving boundary value problems in the presence of a boundary layer. Zh. Vychisl. Mat. i Mat. Fiz. 9, 841–859 (1969, in Russian)
5. Boglaev, I.: On monotone iterative methods for a nonlinear singularly perturbed reaction-diffusion problem. J. Comput. Appl. Math. 162, 445–466 (2004)