1. O'Malley, R. E.,Introduction to Singular Perturbations, Academic Press, New York, New York, 1974.
2. Wasow, W. R.,Asymptotic Expansions for Ordinary Differential Equations, Wiley-Interscience, New York, New York, 1964.
3. Eckhaus, W.,Matched Asymptotic Expansions and Singular Perturbations, North-Holland, Amsterdam, Holland, 1973.
4. Kokotovic, P. V., O'Malley, R. E., andSanutti, P.,Singular Perturbations and Order Reduction in Control Theory?An Overview, Automatica, Vol. 12, No. 2, 1976.
5. Freedman, M. I., andGranoff, B.,Formal Asymptotic Solution of a Singularly Perturbed Nonlinear Optimal Control Problem, Journal of Optimization Theory and Applications, Vol. 19, No. 2, 1976.