@article{articlec61bd062,
title   = {On the finiteness of light rays between a source and an observer on conformally stationary space-times},
author = {Giannoni, Fabio and Masiello, Antonio and Piccione, Paolo},
year = {2001},
doi = {10.1023/A:1010244824124},
journal   = {General Relativity and Gravitation}
}