ZHYHALLO, T. V.; KHARKEVYCH, Yu. I. Approximating properties of biharmonic Poisson operators in the classes $\hat{L}^{\psi}_{\beta, 1}$ . Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 69, n. 5, p. 650–656, 2017. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1724. Acesso em: 5 dec. 2025.