@article{ZNSL_1992_203_a7,
     author = {N. Ya. Kirpichnikova},
     title = {Equations for a~wave front, rays, and a~phase function near a~regular region of the caustic formed by space-time rays},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {92--100},
     publisher = {mathdoc},
     volume = {203},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1992_203_a7/}
}