@incollection{MSMF_1977__51-52__63_0,
     author = {Helffer, Bernard},
     title = {Construction de param\'etrixes pour des op\'erateurs pseudodiff\'erentiels caract\'eristiques sur la r\'eunion de deux c\^ones liss\'es},
     booktitle = {Contributions \`a l'\'etude des op\'erateurs elliptiques et hypoelliptiques},
     series = {M\'emoires de la Soci\'et\'e Math\'ematique de France},
     pages = {63--123},
     publisher = {Soci\'et\'e math\'ematique de France},
     number = {51-52},
     year = {1977},
     doi = {10.24033/msmf.234},
     mrnumber = {57 #856},
     zbl = {0374.35042},
     url = {http://www.numdam.org/articles/10.24033/msmf.234/}
}