ROMANYUK, A. S. Kolmogorov widths and bilinear approximations of the classes of periodic functions of one and many variables. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 70, n. 2, p. 224–235, 2018. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1553. Acesso em: 5 dec. 2025.