@article{00733112,
title = {On the periodic boundary-value problem for systems of second-order nonlinear ordinary differential equations.},
journal = {Georgian Mathematical Journal},
volume = {2},
year = {1995},
pages = {21-36},
doi = {10.1007/BF02257731},
zbl = {0824.34027},
language = {en},
url = {http://dml.mathdoc.fr/item/00733112}
}
Gaprindashvili, G. On the periodic boundary-value problem for systems of second-order nonlinear ordinary differential equations.. Georgian Mathematical Journal, Tome 2 (1995) pp. 21-36. doi : 10.1007/BF02257731. http://gdmltest.u-ga.fr/item/00733112/