1. Introduction to Singular Perturbations;O'Malley,1974
2. Introduction to Perturbation Techniques;Nayfeh,1993
3. Perturbation Methods;Nayfeh,1973
4. Singular Perturbations Methods for Ordinary Differential Equations;O'Malley,1991
5. Fitted Numerical Methods for Singular Perturbation Problems;Miller,1996