Babich, Yu. A., and T. F. Michaylova. 2018. “Approximation of Periodic Functions of Many Variables by functions of Smaller Number of Variables in Orlicz Metric Spaces”. Ukrains’kyi Matematychnyi Zhurnal 70 (8), 1143-48. https://umj.imath.kiev.ua/index.php/umj/article/view/1624.