KONONOVYCH, T. O. Estimate for the Best Approximation of Summable Functions of Several Variables with a Certain Symmetry of Fourier Coefficients. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 55, n. 8, p. 1138–1142, 2003. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3987. Acesso em: 7 apr. 2025.