@article{DE_1977_13_1_a3,
     author = {M. G. Gasymov},
     title = {A certain new spectral problem},
     journal = {Differencialʹnye uravneni\^a},
     pages = {23--28},
     year = {1977},
     volume = {13},
     number = {1},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1977_13_1_a3/}
}