The holomorphic automorphism group of the complex disk.
The homology of Peiffer products of groups.
The Mac Lane method of construction and classification of extensions of cyclic groups by their automorphism groups.
The Number of Stem Covers of an Elementary Abelian p-Group.
The Obstruction theory of Group Extensions and H^3(Q, A) in Abstract Categories
The Recent Generalizations of Colored Symmetry
The Schur multiplier of a generalized Baumslag-Solitar group
The surjectivity problem for one-generator, one-relator extensions of torsion-free groups.
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...
Two problems on varieties of groups generated by wreath products.
Two Theorems on Polycyclic Groups.