1. Ambrosetti, A., Bertotti, M.L.: Homoclinic for second order conservation systems. In: Partial Differential Equations and Related Subjects (Trento, 1990), (Longman Science Technology, Harlow, 1992), pp. 21–37
2. Ambrosetti, A., Coti Zelati, V.: Multiple homoclinic orbits for a class of conservative systems. Rend. Sem. Mat. Univ. Padova 89, 177–194 (1993)
3. Antonacci, F.: Periodic and homoclinic solutions to a class of Hamiltonian systems with indefinite potential in sign. Boll. Un. Mat. Ital. B 10(7), 303–324 (1996)
4. Benhassine, A.: Multiple of homoclinic solutions for a perturbed dynamical systems with combined nonlinearities. Mediter. J. Math. 14, 132 (2017). https://doi.org/10.1007/s00009-017-0930-x
5. Benhassine, A.: Multiplicity of solutions for nonperiodic perturbed fractional Hamiltonian systems. Electron. J. Differ. Equ. 2017(93), 1–15 (2017)