TY  - JOUR
AU  - Carlo Greco
TI  - Periodic trajectories of a class of Lorentz-metrics of a time-dependent gravitational field.
JO  - Mathematische Annalen
PY  - 1990
SP  - 515
EP  - 522
VL  - 287
IS  - 1
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/MAN_1990__287_1_164701/
ID  - MAN_1990__287_1_164701
ER  -