ROMANYUK, A. S. Linear Widths of the Besov Classes of Periodic Functions of Many Variables. I. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 53, n. 5, p. 647–661, 2001. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4287. Acesso em: 5 dec. 2025.