RADZIEVSKAYA, E. I.; RADZIEVSKII, G. V. Estimation of a K-Functional of Higher Order in Terms of a K-Functional of Lower Order. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 55, n. 11, p. 1530–1540, 2003. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4022. Acesso em: 5 dec. 2025.