@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},
     year = {1959},
     number = {2},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1959_2_a18/}
}