@article{GDZPPN002334216,
title = {Periodic trajectories of a class of Lorentz-metrics of a time-dependent gravitational field.},
journal = {Mathematische Annalen},
volume = {287},
year = {1990},
pages = {515-522},
zbl = {0681.53033},
url = {http://dml.mathdoc.fr/item/GDZPPN002334216}
}
Greco, Carlo. Periodic trajectories of a class of Lorentz-metrics of a time-dependent gravitational field.. Mathematische Annalen, Tome 287 (1990) pp. 515-522. http://gdmltest.u-ga.fr/item/GDZPPN002334216/