@incollection{JEDP_1996____A1_0,
     author = {Agmon, Shmuel},
     title = {A perturbation theory of resonances},
     booktitle = {},
     series = {Journ\'ees \'equations aux d\'eriv\'ees partielles},
     eid = {1},
     pages = {1--11},
     publisher = {Ecole polytechnique},
     year = {1996},
     zbl = {0902.47007},
     language = {en},
     url = {http://archive.numdam.org/item/JEDP_1996____A1_0/}
}