Hydden Symmetry approach to the Extended Symmetries in Nonabelian Free   Fermionic and WZNW Models
  Higher spin extensions of nonabelian gauge symmetries for both free fermionic model and WZNW model are considered on a classical level. It is characteristic property of the WZNW model that the higher spin currents which correspond to linear realized higher spin extended affine algebra do not form an invariant space. An extended invariant current space is obtained which allows us to gauge the symmetry. 
Raiko P. Zaikov