Zhyhallo, K. M. and Kharkevych, Y. I. (2011) “Approximation of functions from the classes $C^{\psi}_{\beta, \infty}$ by biharmonic Poisson integrals”, Ukrains’kyi Matematychnyi Zhurnal, 63(7), pp. 939-959. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/2776 (Accessed: 28March2024).