STEPANETS, O. I. Extremal Problems of Approximation Theory in Linear Spaces. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 55, n. 10, p. 1378–1409, 2003. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4008. Acesso em: 5 dec. 2025.