@incollection{JEDP_1987____A4_0,
     author = {Helffer, Bernard and Mohamed, Abderemane},
     title = {Caract\'erisation du spectre essentiel de l'op\'erateur de {Schr\"odinger} avec un champ magn\'etique},
     booktitle = {},
     series = {Journ\'ees \'equations aux d\'eriv\'ees partielles},
     eid = {4},
     pages = {1--6},
     publisher = {Ecole polytechnique},
     year = {1987},
     language = {fr},
     url = {http://archive.numdam.org/item/JEDP_1987____A4_0/}
}