@article{DAN_1960_134_6_a1,
     author = {L. R. Volevich},
     title = {A class of hypoelliptic systems},
     journal = {Doklady Akademii Nauk},
     pages = {1275--1278},
     year = {1960},
     volume = {134},
     number = {6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1960_134_6_a1/}
}