@article{IIMI_2006_37_3_a35,
     author = {P. D. Lebedev and A. A. Uspenskii},
     title = {On the geometry of wave fronts},
     journal = {Izvestiya Instituta Matematiki i Informatiki Udmurtskogo Gosudarstvennogo Universiteta},
     pages = {79--80},
     publisher = {mathdoc},
     volume = {37},
     number = {3},
     year = {2006},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IIMI_2006_37_3_a35/}
}