@article{IM2_1984_22_2_a11,
     author = {A. V. Safonov},
     title = {Information pasts in groups},
     journal = {Izvestiya. Mathematics },
     pages = {393--398},
     publisher = {mathdoc},
     volume = {22},
     number = {2},
     year = {1984},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1984_22_2_a11/}
}