@article{DAN_1963_150_1_a1,
     author = {G. V. Virabyan},
     title = {Spectral properties of operators generated by systems of differential equations of higher order and of {Sobolev} type},
     journal = {Doklady Akademii Nauk},
     pages = {13--16},
     publisher = {mathdoc},
     volume = {150},
     number = {1},
     year = {1963},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1963_150_1_a1/}
}