Free Group Rings and Derived Functors
  An approach to identify the normal subgroups determined by ideals in free group rings with the help of the derived functors of non-additive functors is explored. A similar approach, i.e., via derived functors, for computing limits of functors from the category of free presentations to the category of abelian groups, arising from commutator structure of free groups, is also discussed. 
Roman Mikhailov and Inder Bir S. Passi
math.GR math.AT