@article{IM2_2017_81_2_a5,
     author = {S. A. Stepin and V. V. Fufaev},
     title = {The phase-integral method in a~problem of singular perturbation theory},
     journal = {Izvestiya. Mathematics},
     pages = {359--390},
     year = {2017},
     volume = {81},
     number = {2},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_2017_81_2_a5/}
}