{"DOI":"10.1515/anona-2015-0122","abstract":"AbstractWe prove existence and multiplicity results for periodic solutions of Hamiltonian systems, by the use of a higher dimensional version of the Poincar\u00e9\u2013Birkhoff fixed point theorem. The first part of the paper deals with periodic perturbations of a completely integrable system, while in the second part we focus on some suitable global conditions, so to deal with weakly coupled systems.","author":[{"family":"Fonda"},{"family":"Garrione"},{"family":"Gidoni"}],"id":"unknown","issued":{"date-parts":[[2016,1,1]]},"publisher":"Walter de Gruyter GmbH","title":"Periodic perturbations of Hamiltonian systems","type":"article-journal"}