@article{DAN_1979_247_2_a19,
     author = {M. A. Grinfel'd},
     title = {On the theory of ray method of the wave front investigation in nonlinear problems},
     journal = {Doklady Akademii Nauk},
     pages = {337--340},
     publisher = {mathdoc},
     volume = {247},
     number = {2},
     year = {1979},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1979_247_2_a19/}
}