HNATYUK, Yu. V. Basic properties of the problem of the best simultaneous approximation of several elements. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 48, n. 9, p. 1183–1193, 1996. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5233. Acesso em: 5 dec. 2025.