@incollection{JEDP_1985___1_A5_0, author = {Ikawa, Mitsuru}, title = {On the poles of the scattering matrix for two convex obstacles}, booktitle = {}, series = {Journ\'ees \'equations aux d\'eriv\'ees partielles}, eid = {5}, pages = {1--14}, publisher = {Ecole polytechnique}, number = {1}, year = {1985}, zbl = {0587.35057}, language = {en}, url = {http://archive.numdam.org/item/JEDP_1985___1_A5_0/} }