B. Apanasov: Conformal geometry of discrete groups and manifolds.
De Gruyter 2000, 520p. Eur 148.

3142 Gregori Margulis: Discrete subgroups of semisimple Lie groups.
Springer 1991.

P. Nicholls: The ergodic theory of discrete groups.
Cambridge UP 1989. £ 20.