PichugovS. A. “The Marchaud’s Inequality for Multiple Modules of Continuity in Metric Spaces”. Ukrains’kyi Matematychnyi Zhurnal 71, no. 12 (December 25, 2019): 1712-1716. Accessed December 5, 2020. http://umj.imath.kiev.ua/index.php/umj/article/view/725.