[1] E. P. Doolan. J. J. H. Miller and W. H. A. Schilders, Uniform Numerical Methods for Problems with Initial and Boundary Layers, Boole Press, Dublin(1980).
[2] R. B. Kellogg and A. Tsan, Analysis of some difference approximations fir a singular perturbation problems without turning points, Marh. Comp., 32, 144(1978), 1025-1039
[3] Cai Xin and Lin Pengcheng. Numerical solution of singular pertsrbation problem for self-adjoint ordinary differential equation with mixed boundary value condition, J. Huaqiao University, 11, 4 (1990), 344-352. (in Chinese)
[4] Lin Ping and Su Yucheng, Numerical solution of singular perturbation problem for second order quasilinear ordinary differential equation, Appl. Math. and Mech. (English Ed.). 10, 11 (1989), 1005-1010.
[5] M. H. Protter and H. F. Weinberger, Maximum Principles in Differential Equations, Springer-Verlag, New York (1984)