@article{DAN_1982_265_5_a12,
     author = {B. Yu. Sternin},
     title = {On differential equations of subprincipal type},
     journal = {Doklady Akademii Nauk},
     pages = {1078--1081},
     year = {1982},
     volume = {265},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1982_265_5_a12/}
}