PICHUGOV, S. A. Approximation of periodic functions by constants in the metric spaces $ϕp(L)$. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 46, n. 8, p. 1095–1098, 1994. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5665. Acesso em: 5 dec. 2025.