@article{JEMS_2015_17_4_a7, author = {Amichai Eisenmann}, title = {Counting arithmetic subgroups and subgroup growth of virtually free groups}, journal = {Journal of the European Mathematical Society}, pages = {925--953}, publisher = {mathdoc}, volume = {17}, number = {4}, year = {2015}, doi = {10.4171/jems/522}, url = {http://geodesic.mathdoc.fr/articles/10.4171/jems/522/} }