Kononovych TO. Estimate for the Best Approximation of Summable Functions of Several Variables with a Certain Symmetry of Fourier Coefficients. Ukr. Mat. Zhurn. [Internet]. 2003Aug.25 [cited 2024May9];55(8):1138-42. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/3987