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@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/} }
V. V. Lychagin. Differential equations on two-dimensional manifolds. Izvestiâ vysših učebnyh zavedenij. Matematika, no. 5 (1992), pp. 43-57. http://geodesic.mathdoc.fr/item/IVM_1992_5_a4/