@article{MZM_1991_49_4_a22,
     author = {V. P. Shutyaev},
     title = {Justification of perturbation algorithm in a nonlinear hyperbolic problem},
     journal = {Matemati\v{c}eskie zametki},
     pages = {155--156},
     year = {1991},
     volume = {49},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1991_49_4_a22/}
}