SOSNITSKII, S. P. On instability of the equilibrium state of nonholonomic systems. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 51, n. 3, p. 389–397, 1999. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4622. Acesso em: 5 dec. 2025.