@incollection{JEDP_1988____A1_0, author = {Beals, Richard}, title = {Calcul pseudodiff\'erentiel trois-\'etape}, booktitle = {}, series = {Journ\'ees \'equations aux d\'eriv\'ees partielles}, eid = {1}, pages = {1--4}, publisher = {Ecole polytechnique}, year = {1988}, mrnumber = {975490}, zbl = {0661.35020}, language = {fr}, url = {http://www.numdam.org/item/JEDP_1988____A1_0/} }