@article{CMH_1981__56_139869,
     author = {Peter Thurnheer},
     title = {Zu einem hyperbolischen {Gitterpunktproblem.}},
     journal = {Commentarii mathematici Helvetici},
     pages = {240--271},
     year = {1981},
     volume = {56},
     zbl = {0461.10023},
     url = {http://geodesic.mathdoc.fr/item/CMH_1981__56_139869/}
}