@article{DAN_1985_285_2_a9,
     author = {V. M. Filippov},
     title = {Variational principles for hypoelliptic equations},
     journal = {Doklady Akademii Nauk},
     pages = {302--305},
     publisher = {mathdoc},
     volume = {285},
     number = {2},
     year = {1985},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1985_285_2_a9/}
}