FedorenkoA. S. (1999) “On the best $m$-term trigonometric and orthogonal trigonometric approximations of functions from the classes $L^{Ψ}_{β,ρ}$”, Ukrains’kyi Matematychnyi Zhurnal, 51(12), pp. 1719-1721. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/4776 (Accessed: 2December2024).