@article {1987,
	title = {Symmetry breaking in Hamiltonian systems},
	journal = {J. Differential Equations 67 (1987), no. 2, 165-184},
	number = {SISSA;22/85/M},
	year = {1987},
	publisher = {SISSA Library},
	url = {http://hdl.handle.net/1963/409},
	author = {Antonio Ambrosetti and Vittorio Coti Zelati and Ivar Ekeland}
}
