Extending the Coinvariant Theorems of Chevalley, Shephard--Todd,   Mitchell and Springer
  We extend in several directions invariant theory results of Chevalley, Shephard and Todd, Mitchell and Springer. Their results compare the group algebra for a finite reflection group with its coinvariant algebra, and compare a group representation with its module of relative coinvariants. Our extensions apply to arbitrary finite groups in any characteristic. 
Abraham Broer, Victor Reiner, Larry Smith, Peter Webb