A. S. Romanyuk and S. Y. Yanchenko, “Approximation of classes of periodic functions in one and many variables from the Nikol’skii – Besov and Sobolev spaces”, Ukr. Mat. Zhurn., vol. 74, no. 6, pp. 844–855, Jul. 2022, doi: 10.37863/umzh.v74i6.7141.