@article{DAN_1985_284_5_a1,
     author = {V. S. Belonosov},
     title = {Indices of instability of differential operators},
     journal = {Doklady Akademii Nauk},
     pages = {1037--1041},
     publisher = {mathdoc},
     volume = {284},
     number = {5},
     year = {1985},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1985_284_5_a1/}
}