VAKARCHUK, S. B. Exact values of widths for certain functional classes. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 48, n. 1, p. 133–135, 1996. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5372. Acesso em: 14 apr. 2025.