@article{DAN_1996_346_5_a3,
     author = {L. Z. Fishman},
     title = {On the preservation of the properties of differential equations},
     journal = {Doklady Akademii Nauk},
     pages = {594--596},
     publisher = {mathdoc},
     volume = {346},
     number = {5},
     year = {1996},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1996_346_5_a3/}
}