Development of studies on the exact solution of extremal problems of the theory of best approximation

@article{Babenko1990DevelopmentOS,
title={Development of studies on the exact solution of extremal problems of the theory of best approximation},
author={V. Babenko and A. Ligun},
journal={Ukrainian Mathematical Journal},
year={1990},
volume={42},
pages={1-13}
}

We give a survey of studies on the exact solution of problems of best approximation of function classes by concrete approximating sets, the calculation of widths, and also some similar problems. We pay primary attention to the fundamental results of N. P. Korneichuk with whose name the development of these directions of the theory of approximations is closely associated. The influence of his ideas and the powerful methods he created on the studies of other authors is traced.