@article{702295,
title = {Free vibrations for the equation $u\_{tt}-u\_{xx}+f(u)=0$ with $f$ sublinear},
booktitle = {Equadiff 5},
series = {GDML\_Books},
publisher = {BSB B.G. Teubner Verlagsgesellschaft},
address = {Leipzig},
year = {1982},
pages = {228-230},
mrnumber = {MR0715981},
zbl = {0528.35065},
url = {http://dml.mathdoc.fr/item/702295}
}
Lovicar, Vladimír. Free vibrations for the equation $u_{tt}-u_{xx}+f(u)=0$ with $f$ sublinear, dans Equadiff 5, GDML_Books, (1982), pp. 228-230. http://gdmltest.u-ga.fr/item/702295/