VAKARCHUK, S. B. On exact order estimates of N-widths of classes of functions analytic in a simply connected domain. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 48, n. 4, p. 543–547, 1996. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5318. Acesso em: 5 dec. 2025.