O. P. Bondar', “On the number of critical submanifolds of a function on a manifold”, Ukr. Mat. Zhurn., vol. 45, no. 12, pp. 1702–1705, Dec. 1993, Accessed: Apr. 09, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5979