For citations:

Dautov R.Z. Theorems on direct and inverse approximation by algebraic polynomials and piecewise polynomials in the spaces H^m(a, b) and B^s_2,q(a, b). Izvestiya Vysshikh Uchebnykh Zavedenii. Matematika. 2024;(1):14-34. (In Russ.) https://doi.org/10.26907/0021-3446-2024-1-14-34