1. de Jager E M, Jiang F R. The Theory of Singular Perturbation [M]. Amsterdam: North-Holland Publishing Co, 1996.
2. Barbu L, Morosanu G. Singularly Perturbed Boundary-Value Problems [M]. Basel: Birkhauserm Verlag AG, 2007.
3. Hovhannisyan G, Vulanovic R. Stability inequalities for one-dimensional singular perturbation problems [J]. Nonlinear Stud, 2008, 15(4): 297–322.
4. Graef J R, Kong L. Solutions of second order multi-point boundary value problems[J]. Math Proc Camb Philos Soc, 2008, 145(2): 489–510.
5. Barbu L, Cosma E. Elliptic regularizations for the nonlinear heat equation [J]. J Math Anal Appl, 2009, 351(2): 392–399.