@article{10_1090_S0894_0347_08_00592_4,
     author = {Klainerman, Sergiu and Rodnianski, Igor},
     title = {On the radius of injectivity of null hypersurfaces},
     journal = {Journal of the American Mathematical Society},
     pages = {775--795},
     publisher = {mathdoc},
     volume = {21},
     number = {3},
     year = {2008},
     doi = {10.1090/S0894-0347-08-00592-4},
     url = {http://geodesic.mathdoc.fr/articles/10.1090/S0894-0347-08-00592-4/}
}