@article{GDZPPN002204177,
title = {A potential well theory for the wave equation with a nonlinear boundary condition.},
journal = {Journal f\"ur die reine und angewandte Mathematik},
volume = {374},
year = {1987},
pages = {1-23},
zbl = {0598.35061},
url = {http://dml.mathdoc.fr/item/GDZPPN002204177}
}
Levine, Howard A.; Smith, Richard A. A potential well theory for the wave equation with a nonlinear boundary condition.. Journal für die reine und angewandte Mathematik, Tome 374 (1987) pp. 1-23. http://gdmltest.u-ga.fr/item/GDZPPN002204177/