@article{SEDP_1977-1978____A18_0,
     author = {Melin, A.},
     title = {Free systems of vector fields (d'apr\`es {L.} {H\"ormander} et {A.} {Melin)}},
     journal = {S\'eminaire \'Equations aux d\'eriv\'ees partielles (Polytechnique) dit aussi "S\'eminaire Goulaouic-Schwartz"},
     note = {talk:17},
     pages = {1--7},
     publisher = {Ecole Polytechnique, Centre de Math\'ematiques},
     year = {1977-1978},
     mrnumber = {504146},
     zbl = {0402.58009},
     language = {en},
     url = {http://archive.numdam.org/item/SEDP_1977-1978____A18_0/}
}