Shkapa, V. V. 2015. “Approximating Characteristics of the Classes $L_{β,p}^{ψ}$ of Periodic Functions in the Space $L_q$”. Ukrains’kyi Matematychnyi Zhurnal 67 (8), 1139-50. https://umj.imath.kiev.ua/index.php/umj/article/view/2052.