@article{MAN_1973__203_162444,
     author = {Jan Persson},
     title = {Non-Uniqueness and {Uniqueness} in the {Cauchy} {Problem} at {Simple} {Characteristic} {Points.}},
     journal = {Mathematische Annalen},
     pages = {231--238},
     publisher = {mathdoc},
     volume = {203},
     year = {1973},
     zbl = {0243.35082},
     url = {http://geodesic.mathdoc.fr/item/MAN_1973__203_162444/}
}