@article {1981,
	title = {Recent advances in the study of the existence of periodic orbits of Hamiltonian systems},
	journal = {Advances in Hamiltonian systems (Rome, 1981), 1--22, Ann. CEREMADE, Birkhauser Boston, Boston, MA, 1983.},
	number = {SISSA;8/82/M},
	year = {1981},
	publisher = {SISSA Library},
	url = {http://hdl.handle.net/1963/159},
	author = {Antonio Ambrosetti}
}
