1.
RomanyukA. The best trigonometric and bilinear approximations of the functions of many variables from the classes $B_{p,\theta}^r$. I . Ukr. Mat. Zhurn. [Internet]. 1992Nov.6 [cited 2024Nov.24];44(11):1535-47. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/8257