KALCHUK, I. V.; KHARKEVYCH, Yu. I. I. Approximative properties of biharmonic Poisson integrals in the classes $W^r_{\beta} H^{\alpha}$. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 68, n. 11, p. 1493–1504, 2016. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1936. Acesso em: 5 dec. 2025.