@article{INTG_1988_20_a4,
     author = {V. V. Lychagin},
     title = {Geometric theory of singularities of solutions of nonlinear differential equations},
     journal = {Itogi Nauki i Tekhniki. Seriya Problemy Geometrii. Trudy Geometricheskogo Seminara},
     pages = {207--247},
     publisher = {mathdoc},
     volume = {20},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/INTG_1988_20_a4/}
}