@article{GDZPPN002216280,
title = {Time Periodic Solutions of Nonlinear Wave Equations.},
journal = {Manuscripta mathematica},
volume = {4},
year = {1971},
pages = {165-194},
zbl = {0219.35062},
url = {http://dml.mathdoc.fr/item/GDZPPN002216280}
}
Rabinowitz, Paul H. Time Periodic Solutions of Nonlinear Wave Equations.. Manuscripta mathematica, Tome 4 (1971) pp. 165-194. http://gdmltest.u-ga.fr/item/GDZPPN002216280/