SERDYUK, A. S. Best Approximations and Widths of Classes of Convolutions of Periodic Functions of High Smoothness. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 57, n. 7, p. 946–971, 2005. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3655. Acesso em: 5 dec. 2025.