@article{TM_1990_188_a6,
     author = {A. V. Sobolev and D. R. Yafaev},
     title = {Spectral properties of an abstract scattering matrix},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {125--149},
     year = {1990},
     volume = {188},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TM_1990_188_a6/}
}