[1]
A. S. Romanyuk and V. S. Romanyuk, “Trigonometric and orthoprojection widths of classes of periodic functions of many variables”, Ukr. Mat. Zhurn., vol. 61, no. 10, pp. 1348–1366, Oct. 2009, Accessed: Apr. 13, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3106