@article{DAN_1978_240_2_a1,
     author = {A. N. Bautin},
     title = {On the small parameter method},
     journal = {Doklady Akademii Nauk},
     pages = {253--256},
     year = {1978},
     volume = {240},
     number = {2},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1978_240_2_a1/}
}