@article{10_4153_CMB_2011_119_7,
     author = {Novelli, Carla and Occhetta, Gianluca},
     title = {Manifolds {Covered} by {Lines} and {Extremal} {Rays}},
     journal = {Canadian mathematical bulletin},
     pages = {799--814},
     year = {2012},
     volume = {55},
     number = {4},
     doi = {10.4153/CMB-2011-119-7},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-2011-119-7/}
}