@article{DE_1989_25_10_a31,
     author = {N. A. Chernyavskaya and L. A. Shuster},
     title = {The {WKB} method},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1826--1829},
     year = {1989},
     volume = {25},
     number = {10},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1989_25_10_a31/}
}