@article{GDZPPN002112523, title = {Subgroup growth and congruence subgroups.}, journal = {Inventiones mathematicae}, volume = {121}, year = {1995}, pages = {267-296}, zbl = {0848.20036}, url = {http://dml.mathdoc.fr/item/GDZPPN002112523} }
Lubotzky, Alexander. Subgroup growth and congruence subgroups.. Inventiones mathematicae, Tome 121 (1995) pp. 267-296. http://gdmltest.u-ga.fr/item/GDZPPN002112523/