@article{DE_1994_30_2_a22,
     author = {N. B. Uskova},
     title = {On the spectrum of some classes of differential operators},
     journal = {Differencialʹnye uravneni\^a},
     pages = {350--352},
     publisher = {mathdoc},
     volume = {30},
     number = {2},
     year = {1994},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1994_30_2_a22/}
}