@article{IVM_1958_6_a21,
     author = {A. Z. Petrov},
     title = {lassification of gravitational fields of general form},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {226--232},
     publisher = {mathdoc},
     number = {6},
     year = {1958},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1958_6_a21/}
}