Cherneі N. I. “Criterion of Stable Convexity of a Region in One-Sheeted Conformal Mappings. I ”. Ukrains’kyi Matematychnyi Zhurnal 18, no. 1 (January 29, 1966): 86–91. Accessed April 7, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/8655.