@article{ZNSL_1984_140_a5,
     author = {A. P. Kachalov},
     title = {Space-time ray method for waves of small deformation in a~nonlinear elastic medium},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {61--72},
     year = {1984},
     volume = {140},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1984_140_a5/}
}