@article{DAN_1968_181_2_a4,
     author = {L. B. Zelenko},
     title = {Deficiency index and spectrum of a selfadjoint system of first-order differential equations},
     journal = {Doklady Akademii Nauk},
     pages = {278--281},
     publisher = {mathdoc},
     volume = {181},
     number = {2},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1968_181_2_a4/}
}