A geometrical generalization of the Poincaré method for an investigation of Lagrangian manifolds of slowly perturbed Hamiltonian systems in a neihborhood of a hyperbolic singular point. Neliniini Kolyvannya, [S. l.], v. 3, n. 2, p. 246–255, 2000. Disponível em: https://nosc.imath.kiev.ua/index.php/nosc/article/view/114. Acesso em: 12 apr. 2026.