KOFANOV, V. A. Massiveness of the sets of extremal functions in some problems in approximation theory. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 45, n. 10, p. 1356–1361, 1993. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5940. Acesso em: 5 dec. 2025.