The evolution of radio galaxy emission line regions: Breaking the P-z   degeneracy
  The ionization and kinematic properties of the emission line regions of three subsamples of 6C and 3CR radio galaxies have been compared. The degeneracy between redshift and radio power is broken, and the relative importance of radio power (P), radio size (D) and redshift (z) for the emission line region properties is determined. 
K.J. Inskip, P.N. Best and M.S. Longair