Korneichuk, N. P. “Permutations and Piecewise-Constant Approximation of Continuous Functions of N Variables”. Ukrains’kyi Matematychnyi Zhurnal 50, no. 7 (July 25, 1998): 907–918. Accessed April 14, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/4871.