@article{SM_1992_72_2_a14,
     author = {A. Yu. Ol'shanskii},
     title = {Periodic factor of hyperbolic groups},
     journal = {Sbornik. Mathematics},
     pages = {519--541},
     publisher = {mathdoc},
     volume = {72},
     number = {2},
     year = {1992},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1992_72_2_a14/}
}