1. Brdar, M., Zarin, H., Teofanov, Lj: A singularly perturbed problem with two parameters in two dimensions on graded meshes. Comput. Math. Appl. 72, 2582–2603 (2016)
2. Franz, S., Linß, T., Roos, H.-G.: Superconvergence analysis of the SDFEM for eliptic problems with characteristic layers. Appl. Numer. Math. 58, 1818–1829 (2008)
3. Franz, S., Roos, H.-G.: Error estimation in a balanced norm for a convection-diffusion problem with two different boundary layers. Calcolo 51, 423–440 (2014)
4. Hughes, T.J.R., Brooks, A.: A multidimensional upwind scheme with no crosswind diffusion. In: Hughes, T.J.R. (ed.) Finite Element Methods for Convection Dominated Flows. AMD, vol. 34, pp. 19–35. American Society of Mechanical Engineers, New York (1979)
5. Johnson, C., Navert, U.: An analysis of some finite element methods for advection-diffusion problems. In: Axelsson, O., Frank, L.S., van der Sluis, A. (eds.) Analytical and Numerical Approaches to Asymptotic Problems in Analysis, pp. 99–116. North Holland, Amsterdam (1981)