@article{JEMS_2013_15_2_a5,
     author = {Oihane F. Blanco and Jos\'e M. M. Senovilla and Miguel S\'anchez},
     title = {Structure of second-order symmetric {Lorentzian} manifolds},
     journal = {Journal of the European Mathematical Society},
     pages = {595--634},
     publisher = {mathdoc},
     volume = {15},
     number = {2},
     year = {2013},
     doi = {10.4171/jems/368},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/jems/368/}
}