KonovalovV. N. “Orders of Trigonometric and Kolmogorov Widths May Differ in Power Scale”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 53, no. 11, Nov. 2001, pp. 1575 -1579, https://umj.imath.kiev.ua/index.php/umj/article/view/4378.