@article{Romanyuk_2009, title={Approximative characteristics of the isotropic classes of periodic functions of many variables}, volume={61}, url={https://umj.imath.kiev.ua/index.php/umj/article/view/3036}, abstractNote={Exact-order estimates are obtained for the best orthogonal trigonometric approximations of the Besov $(B_{p,θ}^r)$ and Nukol’skii $(H_p^r )$ classes of periodic functions of many variables in the metric of $L_q , 1 ≤ p, q ≤ ∞$. We also establish the orders of the best approximations of functions from the same classes in the spaces $L_1$ and $L_{∞}$ by trigonometric polynomials with the corresponding spectrum.}, number={4}, journal={Ukrains’kyi Matematychnyi Zhurnal}, author={Romanyuk, A. S.}, year={2009}, month={Apr.}, pages={513-523} }