no. 1
Symmetrization of hyperbolic systems with real constant coefficients
Annali della Scuola Normale Superiore di Pisa - Classe di Scienze, Série 4, Tome 21 (1994) no. 1, pp. 97-130 
@article{ASNSP_1994_4_21_1_97_0,
     author = {Nishitani, Tatsuo},
     title = {Symmetrization of hyperbolic systems with real constant coefficients},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     pages = {97--130},
     year = {1994},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 21},
     number = {1},
     mrnumber = {1276764},
     zbl = {0866.35063},
     language = {en},
     url = {https://www.numdam.org/item/ASNSP_1994_4_21_1_97_0/}
}
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Nishitani, Tatsuo. Symmetrization of hyperbolic systems with real constant coefficients. Annali della Scuola Normale Superiore di Pisa - Classe di Scienze, Série 4, Tome 21 (1994) no. 1, pp. 97-130. https://www.numdam.org/item/ASNSP_1994_4_21_1_97_0/

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