@incollection{MSMF_1973__34__55_0,
     author = {Bolley, Pierre and Camus, Jacques},
     title = {Sur une classe d'op\'erateurs elliptiques et d\'eg\'en\'er\'es \`a plusieurs variables},
     booktitle = {Contributions \`a l'analyse fonctionnelle},
     series = {M\'emoires de la Soci\'et\'e Math\'ematique de France},
     pages = {55--140},
     publisher = {Soci\'et\'e math\'ematique de France},
     number = {34},
     year = {1973},
     doi = {10.24033/msmf.112},
     mrnumber = {58 #1618},
     zbl = {0268.35037},
     url = {http://www.numdam.org/articles/10.24033/msmf.112/}
}