@article{IM2_1987_29_3_a2,
     author = {N. G. Makarov},
     title = {Perturbations of normal operators and stability of the continuous spectrum},
     journal = {Izvestiya. Mathematics },
     pages = {535--558},
     publisher = {mathdoc},
     volume = {29},
     number = {3},
     year = {1987},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1987_29_3_a2/}
}