Romanyuk, A. S., and V. S. Romanyuk. “Approximating Characteristics of the Classes of Periodic Multivariate Functions in the Space $B_{∞,1}$”. Ukrains’kyi Matematychnyi Zhurnal, vol. 71, no. 2, Feb. 2019, pp. 271-82, https://umj.imath.kiev.ua/index.php/umj/article/view/1437.