@incollection{JEDP_1988____A1_0,
     author = {Richard Beals},
     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},
     doi = {10.5802/jedp.345},
     mrnumber = {975490},
     zbl = {0661.35020},
     language = {fr},
     url = {https://proceedings.centre-mersenne.org/articles/10.5802/jedp.345/}
}