@incollection{SB_1978-1979__21__1_0,
     author = {Helffer, Bernard},
     title = {Propagation des singularit\'es pour des probl\`emes aux limites},
     booktitle = {S\'eminaire Bourbaki : vol. 1978/79, expos\'es 525-542},
     series = {S\'eminaire Bourbaki},
     note = {talk:525},
     pages = {1--20},
     publisher = {Springer-Verlag},
     number = {21},
     year = {1980},
     mrnumber = {572414},
     zbl = {0426.35100},
     language = {fr},
     url = {http://www.numdam.org/item/SB_1978-1979__21__1_0/}
}