Shalaev , V. V. “Dimeters in $L_2$ Classes of Differentiated Functions Determined by Continuity Moduli of Higher Orders”. Ukrains’kyi Matematychnyi Zhurnal 43, no. 1 (January 18, 1991): 125–129. Accessed December 6, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/9317.