@article{DE_1994_30_10_a0,
     author = {V. A. Baikov and R. K. Gazizov and N. H. Ibragimov},
     title = {Approximate equivalence transformations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1659--1664},
     publisher = {mathdoc},
     volume = {30},
     number = {10},
     year = {1994},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1994_30_10_a0/}
}