@article{SM_1989_62_1_a1,
     author = {V. E. Pronchatov},
     title = {On an error estimate for the averaging method in a~two-frequency problem},
     journal = {Sbornik. Mathematics},
     pages = {29--40},
     publisher = {mathdoc},
     volume = {62},
     number = {1},
     year = {1989},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1989_62_1_a1/}
}