@article{ZNSL_1988_167_a5,
     author = {N. V. Ivanov},
     title = {Teichm\"uller modular groups and arithmetical groups},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {95--110},
     publisher = {mathdoc},
     volume = {167},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1988_167_a5/}
}