@article{DAN_1964_156_6_a2,
     author = {L. R. Volevich},
     title = {On hypo-elliptic systems with variable coefficients},
     journal = {Doklady Akademii Nauk},
     pages = {1262--1265},
     publisher = {mathdoc},
     volume = {156},
     number = {6},
     year = {1964},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1964_156_6_a2/}
}