@article {2006, title = {Quasi-periodic solutions of completely resonant forced wave equations}, journal = {Comm. Partial Differential Equations 31 (2006) 959 - 985}, number = {SISSA;106/2004/M}, year = {2006}, abstract = {We prove existence of quasi-periodic solutions with two frequencies of completely resonant, periodically forced nonlinear wave equations with periodic spatial boundary conditions. We consider both the cases the forcing frequency is: (Case A) a rational number and (Case B) an irrational number.}, doi = {10.1080/03605300500358129}, url = {http://hdl.handle.net/1963/2234}, author = {Massimiliano Berti and Michela Procesi} }