@article{ZNSL_1974_42_a17,
     author = {N. V. Zepelev},
     title = {The {Caustic} {Problem} {Solution} for the {Elastic} {Medium}},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {255--268},
     publisher = {mathdoc},
     volume = {42},
     year = {1974},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1974_42_a17/}
}