“Solution of the Kolmogorov-Nikol’skii problem for three-harmonic Poisson integrals on classes $C^{\psi}_{\beta,\infty}$” (2014) Transactions of Institute of Mathematics, the NAS of Ukraine, 11(3), pp. 104–127. Available at: https://trim.imath.kiev.ua/index.php/trim/article/view/70 (Accessed: 9 September 2026).