@article{IM2_1995_44_2_a11,
     author = {S. V. Khabirov},
     title = {Extension of differential substitutions},
     journal = {Izvestiya. Mathematics},
     pages = {415--426},
     year = {1995},
     volume = {44},
     number = {2},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1995_44_2_a11/}
}