@article{DAN_1960_131_1_a5,
     author = {M. I. Serov},
     title = {Certain properties of the spectrum of a non-selfadjoint differential operator of the second order},
     journal = {Doklady Akademii Nauk},
     pages = {27--29},
     publisher = {mathdoc},
     volume = {131},
     number = {1},
     year = {1960},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1960_131_1_a5/}
}