@article{DAN_1960_133_4_a16,
     author = {B. L. Livshits},
     title = {Perturbation theory for a simple structure operator},
     journal = {Doklady Akademii Nauk},
     pages = {800--803},
     year = {1960},
     volume = {133},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1960_133_4_a16/}
}