@article{IVM_1992_5_a4,
     author = {V. V. Lychagin},
     title = {Differential equations on two-dimensional manifolds},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {43--57},
     publisher = {mathdoc},
     number = {5},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1992_5_a4/}
}