TelyakovskiiS. A. “Estimation of the Moduli of Continuity of One-Variable Functions in the Metric of $L$ in Terms of Fourier Coefficients”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 46, no. 5, May 1994, pp. 626–632, https://umj.imath.kiev.ua/index.php/umj/article/view/5723.