@article{DAN_1972_206_4_a14,
     author = {Ya. L. Shapiro},
     title = {Reducible {Riemannian} spaces and two-sheeted structures on them},
     journal = {Doklady Akademii Nauk},
     pages = {831--833},
     year = {1972},
     volume = {206},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1972_206_4_a14/}
}