Konovalov, V. N. “Approximation of Sobolev Classes by Their Sections of Finite Dimension”. Ukrains’kyi Matematychnyi Zhurnal 54, no. 5 (May 25, 2002): 647–655. Accessed February 1, 2026. https://umj.imath.kiev.ua/index.php/umj/article/view/4103.