ROMANYUK, A. S. The best trigonometric and bilinear approximations for functions of many variables from the classes $B^r_{p, \theta}$. II. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 45, n. 10, p. 1411–1423, 1993. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5946. Acesso em: 5 dec. 2025.