ZHYHALLO, K. M.; ZHYHALLO, T. V. On the approximation of functions from the Hölder class given on a segment by their biharmonic Poisson operators. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 71, n. 7, p. 915–921, 2019. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1485. Acesso em: 5 dec. 2025.