BabenkoV. F., and SelivanovaS. A. “On the Connection Between Certain Inequalities of the Kolmogorov Type for Periodic and Nonperiodic Functions”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 51, no. 2, Feb. 1999, pp. 147–157, https://umj.imath.kiev.ua/index.php/umj/article/view/4594.