BABENKO, V. F.; GORBENKO, M. E. On the uniqueness of an element of the best $L_1$-approximation for functions with values in a banach space. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 52, n. 1, p. 30–34, 2000. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4393. Acesso em: 11 apr. 2025.