V. V. Savchuk, “Best Linear Methods of Approximation of Functions of the Hardy Class $H_p$”, Ukr. Mat. Zhurn., vol. 55, no. 7, pp. 919–925, Jul. 2003, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3967