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@article{IVM_1964_1_a20, author = {D. E. Chernyi}, title = {Geometry of the {Lagrange} variational problem with a double integral in $X_4$}, journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika}, pages = {153--165}, publisher = {mathdoc}, number = {1}, year = {1964}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/IVM_1964_1_a20/} }
D. E. Chernyi. Geometry of the Lagrange variational problem with a double integral in $X_4$. Izvestiâ vysših učebnyh zavedenij. Matematika, no. 1 (1964), pp. 153-165. http://geodesic.mathdoc.fr/item/IVM_1964_1_a20/