Fedorenko, A. 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), 1719-1721. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/4776