@article{DAN_1978_238_2_a2,
     author = {V. V. Lychagin},
     title = {Nonlinear differential equations and contact geometry},
     journal = {Doklady Akademii Nauk},
     pages = {273--276},
     publisher = {mathdoc},
     volume = {238},
     number = {2},
     year = {1978},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1978_238_2_a2/}
}