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@article{IVM_1969_1_a8, author = {I. V. Parnasskii}, title = {The curvature of {a~semi-Riemannian} space}, journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika}, pages = {53--59}, publisher = {mathdoc}, number = {1}, year = {1969}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/IVM_1969_1_a8/} }
I. V. Parnasskii. The curvature of a~semi-Riemannian space. Izvestiâ vysših učebnyh zavedenij. Matematika, no. 1 (1969), pp. 53-59. http://geodesic.mathdoc.fr/item/IVM_1969_1_a8/