@article{ZNSL_1997_239_a6,
     author = {N. Ya. Kirpichnikova},
     title = {The second approximation of the ray method for calculation of the intensity of the wave front in isotropic
},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {79--94},
     publisher = {mathdoc},
     volume = {239},
     year = {1997},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1997_239_a6/}
}