Estimating the smoothness of the regular component of the solution to a one-dimensional singularly perturbed convection-diffusion equation

The first boundary value problem for a one-dimensional singularly perturbed convection-diffusion equation with variable coefficients on a finite interval is considered. For the regular component of the solution, unimprovable a priori estimates in the Hölder norms are obtained. The estimates are unimprovable in the sense that they fail on any weakening of the estimating norm.