@article{DAN_1990_314_2_a12,
     author = {G. G. Bulychev},
     title = {The characteristic form of equations in the dynamics of},
     journal = {Doklady Akademii Nauk},
     pages = {312--316},
     publisher = {mathdoc},
     volume = {314},
     number = {2},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1990_314_2_a12/}
}