The Schur Multiplicator of SL(2, Z/mZ) and the Congruence Subgroup Property.
The Schur multiplier of a generalized Baumslag-Solitar group
The structure of -free nilpotent groups of step 3.
The subgroups of , or how to compute the table of marks of a finite group.
The surjectivity problem for one-generator, one-relator extensions of torsion-free groups.
The Topological Version of Groups Generated by Reflections.
The triangle groups
The unit group of .
The virtual and universal braids
We study the structure of the virtual braid group. It is shown that the virtual braid group is a semi-direct product of the virtual pure braid group and the symmetric group. Also, it is shown that the virtual pure braid group is a semi-direct product of free groups. From these results we obtain a normal form of words in the virtual braid group. We introduce the concept of a universal braid group. This group contains the classical braid group and has as quotients the singular braid group, virtual...
The virtual Haken conjecture: Experiments and examples.
The width of a power of a free nilpotent group of nilpotency class 2.
The Zassenhaus decomposition for the orthogonal group: properties and applications.
Thompson's group is not minimally almost convex.
Topological dimensions for -groups.
Topology of Finite Graphs.
Trees, valuations, and the Bieri-Neumann-Strebel invariant.
Two short presentations for Lyons' sporadic simple group.
Two-generator subgroups of GL... (...).
Über die absolute Galoisgruppe dyadischer Zahlkörper.
Über die Gelfand-Kirillov-Dimension.