THE SIGNATURE OF D°-D°MIXING AT AN e⁺e^- COLLIDER IS CLEAN

We give a general formula of doubly tagged cross sections for small mixing D°-D°systems. The contamination from doubly Cabibbo suppressed nonleptonic decags to the like–sign events may be cancelled if the neutral pseudoscalar meson pair is in the C-parity odd state which happens in the e⁺e^- collider at ψ" resonance.