@article{CRMATH_2006__343_5_317_0,
     author = {Bekkara, Esmaa and Frances, Charles and Zeghib, Abdelghani},
     title = {On lightlike geometry: isometric actions, and rigidity aspects},
     journal = {Comptes Rendus. Math\'ematique},
     pages = {317--321},
     publisher = {Elsevier},
     volume = {343},
     number = {5},
     year = {2006},
     doi = {10.1016/j.crma.2006.07.007},
     language = {en},
     url = {http://www.numdam.org/articles/10.1016/j.crma.2006.07.007/}
}