KUSHPEL, A. K. Estimates of the Bernstein widths and their analogs. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 45, n. 1, p. 54–59, 1993. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5782. Acesso em: 5 dec. 2025.