A. S. Fedorenko, “On the best $m$-term trigonometric and orthogonal trigonometric approximations of functions from the classes $L^{Ψ}_{β,ρ}$”, Ukr. Mat. Zhurn., vol. 51, no. 12, pp. 1719–1721, Dec. 1999, Accessed: Apr. 09, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4776