LEVIATAN , D.; MOTORNA, O. V.; SHEVCHUK, I. A. No Jackson-type estimates for piecewise $q$-monotone, $q\ge3$, trigonometric approximation. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 74, n. 5, p. 662–675, 2022. DOI: 10.37863/umzh.v74i5.7081. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/7081. Acesso em: 8 dec. 2025.