LASURIYA, R. A. Direct and inverse theorems on approximation of functions defined on a sphere in the space S (p,q)(σ m). Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 59, n. 7, p. 901–911, 2007. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3355. Acesso em: 5 dec. 2025.