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@article{IM2_1988_30_3_a8, author = {A. N. Varchenko}, title = {On~normal forms of nonsmoothness of solutions of hyperbolic equations}, journal = {Izvestiya. Mathematics }, pages = {615--628}, publisher = {mathdoc}, volume = {30}, number = {3}, year = {1988}, language = {en}, url = {http://geodesic.mathdoc.fr/item/IM2_1988_30_3_a8/} }
A. N. Varchenko. On~normal forms of nonsmoothness of solutions of hyperbolic equations. Izvestiya. Mathematics , Tome 30 (1988) no. 3, pp. 615-628. http://geodesic.mathdoc.fr/item/IM2_1988_30_3_a8/