KOGAN, A. M. On the best approximation of classes $W^r H^{ω}$ by algebraic polynomials in the space $L_1$. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 51, n. 11, p. 1456–1466, 1999. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4747. Acesso em: 5 dec. 2025.