@article{MZM_1980_27_4_a1,
     author = {Yu. A. Ignatov},
     title = {Groups of linear fractional transformations generated by three elements},
     journal = {Matemati\v{c}eskie zametki},
     pages = {507--513},
     year = {1980},
     volume = {27},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1980_27_4_a1/}
}