@article{ASNSP_1980_4_7_2_257_0,
     author = {Zeman, Marvin},
     title = {On the uniqueness of the {Cauchy} problem for partial differential operators with multiple characteristics},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     pages = {257--285},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 7},
     number = {2},
     year = {1980},
     mrnumber = {581144},
     zbl = {0478.35006},
     language = {en},
     url = {http://archive.numdam.org/item/ASNSP_1980_4_7_2_257_0/}
}