@article{DAN_1983_268_4_a0,
     author = {N. A. Gusevskii},
     title = {On the fundamental group of a manifold of negative curvature},
     journal = {Doklady Akademii Nauk},
     pages = {777--781},
     publisher = {mathdoc},
     volume = {268},
     number = {4},
     year = {1983},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1983_268_4_a0/}
}