Vyhovs'ka IY, Zelinskii YB, Stefanchuk MV. Generalized convex sets and the problem of shadow. Ukr. Mat. Zhurn. [Internet]. 2015 Dec. 25 [cited 2025 Apr. 24];67(12):1658-66. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/2098