@article{IM2_1987_28_3_a0,
     author = {A. G. Baskakov},
     title = {A~theorem on splitting an operator, and some related questions in the analytic theory of perturbations},
     journal = {Izvestiya. Mathematics },
     pages = {421--444},
     publisher = {mathdoc},
     volume = {28},
     number = {3},
     year = {1987},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1987_28_3_a0/}
}