Vakarchuk SB. Generalized characteristics of smoothness and some extreme problems of the approximation theory of functions in the space $L_2 (R)$. II. Ukr. Mat. Zhurn. [Internet]. 2018Oct.25 [cited 2024Apr.20];70(10):1345-73. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/1640