@article{TM_1983_159_a7,
     author = {S. V. Petras},
     title = {Continuous dependence of poles of the scattering matrix on coefficients of an elliptic operator},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {132--136},
     publisher = {mathdoc},
     volume = {159},
     year = {1983},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TM_1983_159_a7/}
}