@article{702300,
title = {The periodic boundary value problem for some second order ordinary differential equations},
booktitle = {Equadiff 5},
series = {GDML\_Books},
publisher = {BSB B.G. Teubner Verlagsgesellschaft},
address = {Leipzig},
year = {1982},
pages = {256-259},
zbl = {0535.34029},
url = {http://dml.mathdoc.fr/item/702300}
}
Mawhin, Jean. The periodic boundary value problem for some second order ordinary differential equations, dans Equadiff 5, GDML_Books, (1982), pp. 256-259. http://gdmltest.u-ga.fr/item/702300/