@article{DE_1978_14_3_a4,
     author = {A. M. Zverkin},
     title = {The spectrum of a degenerate boundary value problem},
     journal = {Differencialʹnye uravneni\^a},
     pages = {435--441},
     publisher = {mathdoc},
     volume = {14},
     number = {3},
     year = {1978},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1978_14_3_a4/}
}