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@article{DAN_1972_203_1_a10, author = {I. D. Cherkasov}, title = {Tensor conditions for reducibility of elliptic and hyperbolic equations}, journal = {Doklady Akademii Nauk}, pages = {43--45}, publisher = {mathdoc}, volume = {203}, number = {1}, year = {1972}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DAN_1972_203_1_a10/} }
I. D. Cherkasov. Tensor conditions for reducibility of elliptic and hyperbolic equations. Doklady Akademii Nauk, Tome 203 (1972) no. 1, pp. 43-45. http://geodesic.mathdoc.fr/item/DAN_1972_203_1_a10/