RUKASOV, V. I. Approximation of Classes of Analytic Functions by de la Vallée-Poussin Sums. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 55, n. 6, p. 806–816, 2003. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3955. Acesso em: 6 dec. 2025.