@article{PORMA_1994__51_2_47284,
     author = {Frattarolo, Walter},
     title = {A {Hadamard} type theorem for the space-time.},
     journal = {Portugaliae mathematica},
     pages = {257--269},
     publisher = {mathdoc},
     volume = {51},
     number = {2},
     year = {1994},
     zbl = {0824.53075},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1994__51_2_47284/}
}