@article{INTM_1969_5_a0,
     author = {V. F. Butuzov and A. B. Vasil'eva and M. V. Fedoryuk},
     title = {Asymptotic methods in the theory of ordinary differential equations},
     journal = {Itogi nauki i tehniki. Seri\^a, Matemati\v{c}eskij analiz},
     pages = {5--73},
     year = {1969},
     volume = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/INTM_1969_5_a0/}
}