@article{RM_1962_17_4_a11,
     author = {F. A. Neimark},
     title = {On the deficiency index of a~differential operator},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     publisher = {mathdoc},
     volume = {17},
     number = {4},
     year = {1962},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/RM_1962_17_4_a11/}
}