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@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/} }
Jan Persson. Non-Uniqueness and Uniqueness in the Cauchy Problem at Simple Characteristic Points.. Mathematische Annalen, Tome 203 (1973), pp. 231-238. http://geodesic.mathdoc.fr/item/MAN_1973__203_162444/