“…There are considerable works that have contributed to find the periodic solution for perturbations of an integrable problem (see [1,7]). For a perturbed Kepler problem, some of these works apply the method of average of first kind (see, e.g., [3,4,14,25,27]). The technique of combining discrete symmetries of Hamiltonian and the Poincaré continuation method has been considered in other works for twodegree-of-freedom (2-DOF) and three-degree-of-freedom problems (see, e.g., [5,10,25,[31][32][33][34][35]).…”