VlasykH. M. “Order Estimates of the $L_q$-Norms of Generalized Derivatives of the Dirichlet-type kernels With an Arbitrary Choice of Harmonics”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 69, no. 10, Oct. 2017, pp. 1299-0, https://umj.imath.kiev.ua/index.php/umj/article/view/1784.