@article{MZM_1967_1_3_a15,
     author = {A. G. Kostyuchenko},
     title = {Some spectral properties of differential operators},
     journal = {Matemati\v{c}eskie zametki},
     pages = {365--378},
     publisher = {mathdoc},
     volume = {1},
     number = {3},
     year = {1967},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1967_1_3_a15/}
}