PICHUGOV, S. A. On the jackson theorem for periodic functions in spaces with integral metric. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 52, n. 1, p. 122–133, 2000. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4402. Acesso em: 17 apr. 2025.