@article{RM_1977_32_1_a20,
     author = {L. I. Anikeeva},
     title = {The deficiency index of a~certain higher order differential operator},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     year = {1977},
     volume = {32},
     number = {1},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/RM_1977_32_1_a20/}
}