@article{CHEB_2002_3_1_a9,
     author = {Yu. A. Ignatov and A. V. Evtikhova},
     title = {Free groups of linear-fractional transformations},
     journal = {\v{C}eby\v{s}evskij sbornik},
     pages = {78--81},
     publisher = {mathdoc},
     volume = {3},
     number = {1},
     year = {2002},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/CHEB_2002_3_1_a9/}
}