@incollection{JEDP_1982____A3_0,
     author = {Hounie, Jorge},
     title = {On global hypoellipticity of vector fields},
     booktitle = {},
     series = {Journ\'ees \'equations aux d\'eriv\'ees partielles},
     eid = {3},
     pages = {1--8},
     publisher = {Ecole polytechnique},
     year = {1982},
     mrnumber = {83k:35025},
     zbl = {0489.35032},
     language = {en},
     url = {http://archive.numdam.org/item/JEDP_1982____A3_0/}
}