ZALIZKO, V. D. Coconvex approximation of periodic functions. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 59, n. 1, p. 29–43, 2007. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3290. Acesso em: 6 dec. 2025.