PichugovS. A. “Approximation of Compressions of Periodic Functions in the Space $L_p,\; P < 1$”. Ukrains’kyi Matematychnyi Zhurnal 47, no. 12 (December 25, 1995): 1708-1711. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5566.