Maiorov, V. E. “Best Approximation by Ridge Functions in $L_p$-Spaces”. Ukrains’kyi Matematychnyi Zhurnal 62, no. 3 (March 25, 2010): 396–408. Accessed April 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/2875.