@article{MZM_1976_20_3_a5,
     author = {T. M. Kerimov and V. A. Kondrat'ev},
     title = {The spectrum of an elliptic operator of second order},
     journal = {Matemati\v{c}eskie zametki},
     pages = {351--358},
     publisher = {mathdoc},
     volume = {20},
     number = {3},
     year = {1976},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1976_20_3_a5/}
}