1. R. Bartolo—A. Masiello,On the existence of infinitely many trajectories for a class of static Lorentzian manifolds like Schwarzschild and Reissner-Nordström space-times, J. Math. Anal. Appl.,199 (1996), pp. 14–38.
2. V. Benci,Closed geodesics for the Jacobi metric and periodic solutions of prescribed energy of natural Hamiltonian systems, Ann. Inst. Henri Poincaré, Anal. non lin.,1 (1984), pp. 401–412.
3. V. Benci— D. Fortunato,Periodic trajectories for the Lorentz metric of a static gravitational field, Proc. on «Variational Methods» (H. Berestycki— J. M. Coron— I. Ekeland, Eds.) Paris (1988), pp. 413–429.
4. V. Benci— D. Fortunato— F. Giannoni,On the existence of periodic trajectories in static Lorentz manifolds with singular boundary, Nonlinear Analysis, a Tribute in honour of G. Prodi, Quaderni della Scuola Normale Superiore, Pisa (A. Ambrosetti— A. Marino, Eds.) (1991), pp. 109–133.
5. V. Benci—D. Fortunato—F. Giannoni,On the existence of geodesics in static Lorentz manifolds with singular boundary, Ann. Sc. Normale Sup. Pisa Serie IV,XIX (1992), pp. 255–289.