@article{IVM_1987_6_a10,
     author = {Ya. L. Shapiro and V. A. Igoshin},
     title = {A geodesic field of directions in the general theory of relativity},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {72--76},
     year = {1987},
     number = {6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1987_6_a10/}
}