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@article{IVM_1959_2_a18, author = {A. Z. Petrov}, title = {On symmetric gravitational fields}, journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika}, pages = {189--197}, publisher = {mathdoc}, number = {2}, year = {1959}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/IVM_1959_2_a18/} }
A. Z. Petrov. On symmetric gravitational fields. Izvestiâ vysših učebnyh zavedenij. Matematika, no. 2 (1959), pp. 189-197. http://geodesic.mathdoc.fr/item/IVM_1959_2_a18/