Continuation of periodic orbits in symmetric Hamiltonian and conservative systems J. Galan-Vioque, F.J.M. Almaraz and E.F. Macías Eur. Phys. J. Special Topics, 223 13 (2014) 2705-2722 Published online: 10 December 2014 DOI: 10.1140/epjst/e2014-02287-6