1.
Kononovych TO. Estimate for the Best Approximation of Summable Functions of Two Variables in Terms of Fourier Coefficients. Ukr. Mat. Zhurn. [Internet]. 2004 Jan. 25 [cited 2025 Apr. 7];56(1):51-69. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/3727