@article{PORMA_1988__45_2_115626,
     author = {Carvalho e Silva, Jaime},
     title = {A sufficient condition for the well posedness of a {Goursat} problem},
     journal = {Portugaliae mathematica},
     pages = {221--228},
     publisher = {mathdoc},
     volume = {45},
     number = {2},
     year = {1988},
     mrnumber = {0952540},
     zbl = {0666.35017},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1988__45_2_115626/}
}