RukasovV. I., & StepanetsO. I. (2003). Best “Continuous” $n$-Term Approximations in the Spaces $S_\phi ^p$. Ukrains’kyi Matematychnyi Zhurnal, 55(5), 663-670. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/3941