@article{SEDP_1980-1981____A20_0,
     author = {Tartakoff, D.},
     title = {Hypoellipticit\'e analytique pour des op\'erateurs \`a caract\'eristiques multiples - {D\'emonstration} \'el\'ementaire},
     journal = {S\'eminaire \'Equations aux d\'eriv\'ees partielles (Polytechnique) dit aussi "S\'eminaire Goulaouic-Schwartz"},
     note = {talk:18 bis},
     pages = {1--13},
     publisher = {Ecole Polytechnique, Centre de Math\'ematiques},
     year = {1980-1981},
     mrnumber = {657988},
     zbl = {0491.35041},
     language = {fr},
     url = {http://archive.numdam.org/item/SEDP_1980-1981____A20_0/}
}