@incollection{JEDP_1981____A12_0,
     author = {Mohamed, Abderemane},
     title = {\'Etude spectrale d'op\'erateurs hypoelliptiques \`a caract\'eristiques multiples},
     booktitle = {},
     series = {Journ\'ees \'equations aux d\'eriv\'ees partielles},
     eid = {12},
     pages = {1--7},
     publisher = {Ecole polytechnique},
     year = {1981},
     zbl = {0495.58028},
     language = {fr},
     url = {http://archive.numdam.org/item/JEDP_1981____A12_0/}
}