“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”, НК, vol. 3, no. 2, pp. 246–255, Jun. 2000, Accessed: Jan. 22, 2026. [Online]. Available: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/114