@article{DAN_1985_283_5_a10,
     author = {G. G. Kazaryan},
     title = {A numerical characteristic of linear differential operators with},
     journal = {Doklady Akademii Nauk},
     pages = {1068--1072},
     year = {1985},
     volume = {283},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1985_283_5_a10/}
}