[1]
V. V. Shkapa, “Best trigonometric and bilinear approximations for the classes of $(ψ, β)$ -differentiable periodic functions”, Ukr. Mat. Zhurn., vol. 68, no. 3, pp. 386–399, Mar. 2016, Accessed: Feb. 16, 2026. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/1846