V. L. Mel’nik, “Investigation of smoothness conditions on the boundary for the strong linear convexity of a domain”, Ukr. Mat. Zhurn., vol. 51, no. 12, pp. 1710–1713, Dec. 1999, Accessed: Apr. 07, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4774