GIANNONI, F.; MASIELLO, A. Morse relations for geodesics on stationary Lorentzian manifolds with boundary. Topological Methods in Nonlinear Analysis, [S. l.], v. 6, n. 1, p. 1–30, 1995. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.1995.029. Acesso em: 29 mar. 2024.