Numerical Methods for Singularly Perturbed Differential Equations

The analysis of singular perturbed differential equations began early in this century, when approximate solutions were constructed from asymptotic ex­ pansions. (Preliminary attempts appear in the nineteenth century [vD94].) This technique has flourished since the mid-1960s. Its principal ideas and methods are described in several textbooks. Nevertheless, asymptotic ex­ pansions may be impossible to construct or may fail to simplify the given problem; then numerical approximations are often the