@article{GDZPPN00220830X,
title = {A spectral proof of Rademacher's conjecture for congruence subgroups of the modular group.},
journal = {Journal f\"ur die reine und angewandte Mathematik},
volume = {416},
year = {1991},
pages = {113-116},
zbl = {0709.11031},
url = {http://dml.mathdoc.fr/item/GDZPPN00220830X}
}
Zograf, P. A spectral proof of Rademacher's conjecture for congruence subgroups of the modular group.. Journal für die reine und angewandte Mathematik, Tome 416 (1991) pp. 113-116. http://gdmltest.u-ga.fr/item/GDZPPN00220830X/