BABENKO, V. V.; BABENKO, V. F.; POLISHCHUK, M. V. Approximation of some classes of set-valued periodic functions by generalized trigonometric polynomials. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 68, n. 4, p. 449–459, 2016. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1851. Acesso em: 14 apr. 2025.