On the determination of the relative sign of a1 and a2 from polarization measurements in Bu− → ϱ−D∗o decay

We point out that polarization measurements such as the longitudinal fraction and the transverse left-right asymmetry in the Bauer-Stech-Wirbel (BSW) Class III processes involving two final vector mesons, B− → ϱ−D∗o taken as an example, are useful in the determination of the relative sign as well as the relative magnitudes of the coefficients a1 and a2.