MUSSO, Monica; PEJSACHOWICZ, Jacobo; PORTALURI, Alessandro. A Morse index theorem for perturbed geodesics on semi-Riemannian manifolds. Topological Methods in Nonlinear Analysis, [S. l.], v. 25, n. 1, p. 69–99, 2005. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2005.004. Acesso em: 1 jul. 2025.