L. N. Bozhukha, “On a Jackson-Type Inequality in the Approximation of a Function by Linear Summation Methods in the Space $L_2$”, Ukr. Mat. Zhurn., vol. 55, no. 4, pp. 537–545, Apr. 2003, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3927