@article{DE_1992_28_8_a7,
     author = {V. V. Filippov},
     title = {On an investigation of ordinary differential equations ``with respect to the first approximation''},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1351--1355},
     publisher = {mathdoc},
     volume = {28},
     number = {8},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1992_28_8_a7/}
}