@article {2008, title = {Multiple bound states for the Schroedinger-Poisson problem}, journal = {Commun. Contemp. Math. 10 (2008) 391-404}, year = {2008}, doi = {10.1142/S021919970800282X}, url = {http://hdl.handle.net/1963/2679}, author = {Antonio Ambrosetti and David Ruiz} }