@incollection{JEDP_1996____A1_0, author = {Shmuel Agmon}, 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 = {https://proceedings.centre-mersenne.org/item/JEDP_1996____A1_0/} }