Sosnitskii, S. P. “On Instability of the Equilibrium State of Nonholonomic Systems”. Ukrains’kyi Matematychnyi Zhurnal 51, no. 3 (March 25, 1999): 389–397. Accessed February 17, 2026. https://umj.imath.kiev.ua/index.php/umj/article/view/4622.