SERDYUK, A. S. On the best approximation of classes of convolutions of periodic functions by trigonometric polynomials. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 47, n. 9, p. 1261–1265, 1995. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5526. Acesso em: 6 dec. 2025.