Geometry, Isometries and Gauging of (2,1) Heterotic Sigma-Models
  The geometry of (2,1) supersymmetric sigma-models is reviewed and the conditions under which they have isometry symmetries are analysed. Certain potentials are constructed that play an important role in the gauging of such symmetries. The gauged action is found for a special class of models. 
M. Abou Zeid and C. M. Hull