@article{DE_1977_13_1_a15,
     author = {M. Otelbaev},
     title = {A criterion for discreteness of the spectrum for a certain degenerate operator, and certain imbedding theorems},
     journal = {Differencialʹnye uravneni\^a},
     pages = {111--120},
     publisher = {mathdoc},
     volume = {13},
     number = {1},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1977_13_1_a15/}
}