@article{SMJ2_2008_34_1_a5,
     author = {Bachelot, Alain},
     title = {Global {Waves} with {Non-Positive} {Energy} in {General} {Relativity}},
     journal = {Serdica Mathematical Journal},
     pages = {127--154},
     publisher = {mathdoc},
     volume = {34},
     number = {1},
     year = {2008},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SMJ2_2008_34_1_a5/}
}