S. P. Sosnitskii, “On instability of the equilibrium state of nonholonomic systems”, Ukr. Mat. Zhurn., vol. 51, no. 3, pp. 389–397, Mar. 1999, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4622