AkishevG. “Trigonometric Widths of the Nikol’skii–Besov Classes in the Lebesgue Space With Mixed Norm”. Ukrains’kyi Matematychnyi Zhurnal 66, no. 6 (June 25, 2014): 723–732. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/2173.