Vyhovs’ka, I. Yu., and Yu. B. Zelinskii. “Criterion for Convexity of a Domain of a Euclidean Space”. Ukrains’kyi Matematychnyi Zhurnal 60, no. 5 (May 25, 2008): 709–711. Accessed May 3, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3189.