IGNATYEV, A. O. Application of the direct Lyapunov’s method to the investigation of integral sets . Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 44, n. 10, p. 1342–1348, 1992. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8230. Acesso em: 14 apr. 2025.