@article{SEDP_1980-1981____A1_0,
     author = {M\'etivier, G.},
     title = {Hypoellipticit\'e d'op\'erateurs \`a caract\'eristiques multiples},
     journal = {S\'eminaire \'Equations aux d\'eriv\'ees partielles (Polytechnique) dit aussi "S\'eminaire Goulaouic-Schwartz"},
     note = {talk:1},
     pages = {1--13},
     publisher = {Ecole Polytechnique, Centre de Math\'ematiques},
     year = {1980-1981},
     zbl = {0491.35040},
     language = {fr},
     url = {http://www.numdam.org/item/SEDP_1980-1981____A1_0/}
}