Optimal observables for measuring three-gauge-boson couplings in $e^+   e^- \to W^+ W^-$
  Observables with optimised sensitivity to the $WWZ$ and $WW\gamma$-couplings in $e^+ e^- \to W^+ W^-$ are investigated. They allow for separate studies of CP violation and of absorptive parts in the amplitude. We have calculated expected statistical errors on extracted couplings at $\sqrt{s} = 500 GeV$, with unpolarised or longitudinally polarised beams. 
M. Diehl and O. Nachtmann