IGNAT'EV, A. O. On the existence of a lyapunov function as a quadratic form for impulsive systems of linear differential equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 62, n. 11, p. 1451–1458, 2010. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2970. Acesso em: 5 dec. 2025.