no. 1
Integral representation of solutions of first-order linear partial differential equations, I
Annali della Scuola Normale Superiore di Pisa - Classe di Scienze, Série 4, Tome 3 (1976) no. 1, pp. 1-35. 
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     title = {Integral representation of solutions of first-order linear partial differential equations, {I}},
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Treves, François. Integral representation of solutions of first-order linear partial differential equations, I. Annali della Scuola Normale Superiore di Pisa - Classe di Scienze, Série 4, Tome 3 (1976) no. 1, pp. 1-35. http://archive.numdam.org/item/ASNSP_1976_4_3_1_1_0/

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