@article{DAN_1957_115_1_a7,
     author = {A. G. Kostyuchenko},
     title = {On the spectral properties of elliptical operators},
     journal = {Doklady Akademii Nauk},
     pages = {34--37},
     publisher = {mathdoc},
     volume = {115},
     number = {1},
     year = {1957},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1957_115_1_a7/}
}