@article {2003, title = {Periodic solutions of nonlinear wave equations with general nonlinearities}, journal = {Comm.Math.Phys. 243 (2003) no.2, 315}, number = {SISSA;78/2002/M}, year = {2003}, publisher = {SISSA Library}, doi = {10.1007/s00220-003-0972-8}, url = {http://hdl.handle.net/1963/1648}, author = {Massimiliano Berti and Philippe Bolle} }