ZelinskiiYu. B., and MomotI. V. “On $(n, m)$-Convex Sets”. Ukrains’kyi Matematychnyi Zhurnal 53, no. 3 (March 25, 2001): 422-427. Accessed November 22, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4263.