A class of second-order evolution equations with double characteristics
Annali della Scuola Normale Superiore di Pisa - Classe di Scienze, Serie 4, Volume 3 (1976) no. 2, p. 187-229 
@article{ASNSP_1976_4_3_2_187_0,
     author = {Gilioli, Antonio},
     title = {A class of second-order evolution equations with double characteristics},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 3},
     number = {2},
     year = {1976},
     pages = {187-229},
     zbl = {0327.35018},
     mrnumber = {437961},
     language = {en},
     url = {http://www.numdam.org/item/ASNSP_1976_4_3_2_187_0}
}

Gilioli, Antonio. A class of second-order evolution equations with double characteristics. Annali della Scuola Normale Superiore di Pisa - Classe di Scienze, Serie 4, Volume 3 (1976) no. 2, pp. 187-229. http://www.numdam.org/item/ASNSP_1976_4_3_2_187_0/

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