R. A. Lasuriya, “Direct and inverse theorems on approximation of functions defined on a sphere in the space S (p,q)(σ m)”, Ukr. Mat. Zhurn., vol. 59, no. 7, pp. 901–911, Jul. 2007, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3355