@article{DAN_1963_152_4_a12,
     author = {F. G. Maslova},
     title = {A problem in the spectral theory of differential operators},
     journal = {Doklady Akademii Nauk},
     pages = {820},
     publisher = {mathdoc},
     volume = {152},
     number = {4},
     year = {1963},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1963_152_4_a12/}
}