Near Frattini subgroups of residually finite generalized free products of groups.
New a-T-menable HNN-extensions.
Nielsen methods in groups with a length function.
Nielsen reduction in free groups with operators
Non-abelian group structure on the Urysohn universal space
We prove that there exists a non-abelian group structure on the Urysohn universal metric space. More precisely, we introduce a variant of the Graev metric that enables us to construct a free group with countably many generators equipped with a two-sided invariant metric that is isometric to the rational Urysohn space. We list several related open problems.
Non-amenable finitely presented torsion-by-cyclic groups
Normal-convexity and equations over groups.
Note on a question of Reinhold Baer on pregroups
Note on a Question of Reinhold Baer on Pregroups II
Note on generalizing pregroups.