@article{GDZPPN002101645,
title = {On cusp forms for co-finite subgroups of PSL(2, IR).},
journal = {Inventiones mathematicae},
volume = {82},
year = {1985},
pages = {339-364},
zbl = {0558.10017},
url = {http://dml.mathdoc.fr/item/GDZPPN002101645}
}
Sarnak, P.; Phillips, R.S. On cusp forms for co-finite subgroups of PSL(2, IR).. Inventiones mathematicae, Tome 82 (1985) pp. 339-364. http://gdmltest.u-ga.fr/item/GDZPPN002101645/