SHUMEIKO, A. A. On approximation of functions from below by splines of the best approximation with free nodes. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 52, n. 4, p. 512–523, 2000. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4440. Acesso em: 5 dec. 2025.