@incollection{JEDP_1976____A12_0,
     author = {Persson, Jan},
     title = {The {Cauchy} problem and {Hadamard's} example},
     booktitle = {},
     series = {Journ\'ees \'equations aux d\'eriv\'ees partielles},
     eid = {12},
     pages = {1--3},
     publisher = {Ecole polytechnique},
     year = {1976},
     language = {en},
     url = {http://archive.numdam.org/item/JEDP_1976____A12_0/}
}