  We show that the CP-violating phases \beta and \beta' can respectively be
determined from the time-dependent measurements of B_d \to D^*\pmD^\mp and B_s
\to D^*\pm_sD^\mp_s decays, whose final states are non-CP eigenstates. The
penguin contributions to the mixing-induced interference quantities are
expected to be about 4% or smaller. We also point out two observables of O(1),
which are pure functions of decay constants and form-factors, for a clean test
of the factorization hypothesis in neutral-B decays into two heavy charmed
mesons.
