@article{DE_1987_23_2_a9,
     author = {A. M. Samoilenko},
     title = {On the question of the justification of the averaging method for multifrequency oscillating systems},
     journal = {Differencialʹnye uravneni\^a},
     pages = {267--278},
     year = {1987},
     volume = {23},
     number = {2},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1987_23_2_a9/}
}