@article{DE_1984_20_2_a22,
     author = {L. A. Kalyakin},
     title = {Asymptotic integration of hyperbolic equations with weakly nonlinear perturbation},
     journal = {Differencialʹnye uravneni\^a},
     pages = {351--353},
     year = {1984},
     volume = {20},
     number = {2},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1984_20_2_a22/}
}