RomanyukA. S. “Entropy Numbers and the Widths of the Classes $B_{p,θ}^r$ of Periodic functions of Many Variables”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 68, no. 10, Oct. 2016, pp. 1403-17, http://umj.imath.kiev.ua/index.php/umj/article/view/1928.