S. P. Voitenko, “Best $M$-Term trigonometric approximations of the classes $B^{Ω}_{p,θ}$ of periodic functions of many variables”, Ukr. Mat. Zhurn., vol. 61, no. 9, pp. 1189–1199, Sep. 2009, Accessed: Apr. 09, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3091