KOPACHEVSKY, N. D. On stability and instability of small motions of hydrodynamical systems. Methods of Functional Analysis and Topology, [S. l.], v. 13, n. 2, p. 152–168, 2007. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/345. Acesso em: 16 dec. 2025.