@article{DE_1986_22_3_a24,
     author = {S. A. Mazanik},
     title = {The structure of the approximation function for a linear differential equation},
     journal = {Differencialʹnye uravneni\^a},
     pages = {542--545},
     year = {1986},
     volume = {22},
     number = {3},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1986_22_3_a24/}
}