  We provide succinct covariant amplitude decompositions of 2-body weak
hadronic decays, with which to compare data, including exclusive rates,
helicity amplitudes and polarizations. For weak decays, the systematic
dependence of these amplitudes on masses and quantum numbers of participating
particles are determined within a factor of about two by the CKM angles and the
Fermi constant so theoretical models need to be much more accurate if they are
to be convincing.
