On pseudosymmetric systems with one space variable
Annali della Scuola Normale Superiore di Pisa - Classe di Scienze, Serie 4, Volume 30 (2001) no. 3-4, p. 661-679 
@article{ASNSP_2001_4_30_3-4_661_0,
     author = {Nishitani, Tatsuo and Spagnolo, Sergio},
     title = {On pseudosymmetric systems with one space variable},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 30},
     number = {3-4},
     year = {2001},
     pages = {661-679},
     zbl = {1030.35111},
     mrnumber = {1896081},
     language = {en},
     url = {http://www.numdam.org/item/ASNSP_2001_4_30_3-4_661_0}
}

Nishitani, Tatsuo; Spagnolo, Sergio. On pseudosymmetric systems with one space variable. Annali della Scuola Normale Superiore di Pisa - Classe di Scienze, Serie 4, Volume 30 (2001) no. 3-4, pp. 661-679. http://www.numdam.org/item/ASNSP_2001_4_30_3-4_661_0/

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