  In a recent paper on SU(16) grand unification, because of the presence of
intermediate-energy gauge groups containing products of U(1) factors which are
not orthogonal among themselves, the renormalization-group treatment has a few
small errors. I correct it. I emphasize that one should not switch gauge
couplings at the various thresholds. It is easier, and it avoids errors, to use
throughout the gauge couplings of the standard model, and compute at each
threshold, in the usual way, the extra contributions to the beta functions from
the extra non-decoupled fields. I also point out that the SU(16) grand
unification theory, due to the large number of scalars present in it, is not
asymptotically free. It becomes a strong-coupling theory at energies only
slightly larger than the unification scale.
