Romanyuk, A. S. and Romanyuk, V. S. (2009) “Trigonometric and orthoprojection widths of classes of periodic functions of many variables”, Ukrains’kyi Matematychnyi Zhurnal, 61(10), pp. 1348-1366. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/3106 (Accessed: 29March2024).