KALCHUK, I. V.; KHARKEVYCH, Yu. I. Asymptotics of the values of approximations in the mean for classes of differentiable functions by using biharmonic Poisson integrals. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 59, n. 8, p. 1105–1115, 2007. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3373. Acesso em: 14 apr. 2025.