PICHUGOV, S. A. Lower bounds for the deviations of the best linear methods of approximation of continuous functions by trigonometric polynomials. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 64, n. 5, p. 662–673, 2012. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2606. Acesso em: 5 dec. 2025.