@article{SM_1972_16_1_a3,
     author = {V. M. Babich},
     title = {On the asymptotics of {Green's} functions for certain wave problems. {II.~Nonstationary} case},
     journal = {Sbornik. Mathematics},
     pages = {45--59},
     year = {1972},
     volume = {16},
     number = {1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1972_16_1_a3/}
}