Vakarchuk, S. B. 2014. “Jackson-Type Inequalities for the Special Moduli of Continuity on the Entire Real Axis and the Exact Values of Mean $ν$ - Widths for the Classes of Functions in the Space $L_2 (ℝ)$”. Ukrains’kyi Matematychnyi Zhurnal 66 (6), 740–766. https://umj.imath.kiev.ua/index.php/umj/article/view/2175.