SERDYUK, A. S.; STEPANETS, O. I. Direct and Inverse Theorems in the Theory of Approximation of Functions in the Space $S^p$. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 54, n. 1, p. 106–124, 2002. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4044. Acesso em: 6 dec. 2025.