Constraints on Four Fermion Contact Interactions from Precise   Electroweak Measurements
  We establish constraints on a general four-fermion contact interaction from precise measurements of electroweak parameters. We compute the one-loop contribution for the leptonic $Z$ width, anomalous magnetic, weak-magnetic, electric and weak dipole moments of leptons in order to extract bounds on the energy scale of these effective interactions. 
M. C. Gonzalez-Garcia, A. Gusso and S. F. Novaes