@article{DAN_1987_294_1_a13,
     author = {A. L. Litvin and I. D. Tsvankin},
     title = {Nonstationary wave fields of point sources and},
     journal = {Doklady Akademii Nauk},
     pages = {54--58},
     publisher = {mathdoc},
     volume = {294},
     number = {1},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1987_294_1_a13/}
}