@article{SEDP_1988-1989____A2_0,
     author = {Helffer, B.},
     title = {Formes normales pour des op\'erateurs pseudodiff\'erentiels semiclassiques en dimension 1},
     journal = {S\'eminaire \'Equations aux d\'eriv\'ees partielles (Polytechnique) dit aussi "S\'eminaire Goulaouic-Schwartz"},
     note = {talk:2},
     pages = {1--12},
     publisher = {Ecole Polytechnique, Centre de Math\'ematiques},
     year = {1988-1989},
     mrnumber = {1032278},
     zbl = {0699.35273},
     language = {fr},
     url = {http://www.numdam.org/item/SEDP_1988-1989____A2_0/}
}