@article{article050c734b,
title   = {Periodic geodesics and geometry of compact Lorentzian manifolds with a Killing vector field},
author = {Flores, Jose Luis and Javaloyes, Miguel Angel and Piccione, Paolo},
year = {2011},
doi = {10.1007/s00209-009-0617-5},
journal   = {Mathematische Zeitschrift}
}