@article{IVM_1999_7_a8,
     author = {A. M. Sidorov},
     title = {On a~class of perturbed operators},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {61--66},
     publisher = {mathdoc},
     number = {7},
     year = {1999},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1999_7_a8/}
}