In order to observe a signal of possible CP violation in top-quark couplings,
we have studied energy correlation of the final leptons in e+e−→ttˉ→ℓ+ℓ−X/ℓ±X at future linear colliders. Applying the
recently-proposed optimal method, we have compared the statistical
significances of CP-violation-parameter determination using double- and
single-lepton distributions. We have found that the single-lepton-distribution
analysis is more advantageous.Comment: Final version (to appear in Phys.Lett.B