@article{DAN_1963_153_4_a4,
     author = {F. G. Maksudov},
     title = {On the spectrum of singular non-selfadjoint differential operators of order~$2n$},
     journal = {Doklady Akademii Nauk},
     pages = {758--761},
     publisher = {mathdoc},
     volume = {153},
     number = {4},
     year = {1963},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1963_153_4_a4/}
}