@article{MZM_1979_25_3_a10,
     author = {A. N. Kochubei},
     title = {Symmetric operators and nonclassical spectral problems},
     journal = {Matemati\v{c}eskie zametki},
     pages = {425--434},
     publisher = {mathdoc},
     volume = {25},
     number = {3},
     year = {1979},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1979_25_3_a10/}
}