@article{DAN_1977_236_4_a15,
     author = {O. N. Naida},
     title = {Ray approximation in the acoustics of inhomogeneous anisotropic media},
     journal = {Doklady Akademii Nauk},
     pages = {842--845},
     publisher = {mathdoc},
     volume = {236},
     number = {4},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1977_236_4_a15/}
}