no. 1
The parametrix of regular hypoelliptic boundary value problems
Annali della Scuola Normale Superiore di Pisa - Scienze Fisiche e Matematiche, Série 3, Tome 26 (1972) no. 1, pp. 247-268 
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     author = {Barros-Neto, J.},
     title = {The parametrix of regular hypoelliptic boundary value problems},
     journal = {Annali della Scuola Normale Superiore di Pisa - Scienze Fisiche e Matematiche},
     pages = {247--268},
     year = {1972},
     publisher = {Scuola normale superiore},
     volume = {Ser. 3, 26},
     number = {1},
     mrnumber = {477425},
     zbl = {0235.35026},
     language = {en},
     url = {https://www.numdam.org/item/ASNSP_1972_3_26_1_247_0/}
}
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Barros-Neto, J. The parametrix of regular hypoelliptic boundary value problems. Annali della Scuola Normale Superiore di Pisa - Scienze Fisiche e Matematiche, Série 3, Tome 26 (1972) no. 1, pp. 247-268. https://www.numdam.org/item/ASNSP_1972_3_26_1_247_0/

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