@article{SM_1995_80_2_a12,
     author = {Yu. A. Konyaev},
     title = {On a method of studying certain problems in perturbation theory},
     journal = {Sbornik. Mathematics},
     pages = {507--517},
     publisher = {mathdoc},
     volume = {80},
     number = {2},
     year = {1995},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1995_80_2_a12/}
}