1. Alfréd Rényi Institute of Mathematics, Hungarian Academy of Sciences, POB 127, Budapest H-1364, Hungary
2. MTA Rényi Intézet Lendület Groups and Graphs Research Group
3. Institute for Advanced Study, Princeton, NJ, USA
4. MTA Rényi Intézet Lendület Automorphic Research Group
5. Central European University, Nador u. 9, Budapest H-1051, Hungary