SMAZHENKO, I. V. Weighted Moduli of Smoothness and Sign-Preserving Approximation. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 57, n. 3, p. 400–420, 2005. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3608. Acesso em: 6 dec. 2025.