  It is proved for Abelian groups that the Reidemeister coincidence number of
two endomorphisms $\phi$ and $\psi$ is equal to the number of coincidence
points of $\wh\phi$ and $\wh\psi$ on the unitary dual, if the Reidemeister
number is finite. An affirmative answer to the bitwisted Dehn conjugacy problem
for almost polycyclic groups is obtained. Finally we explain why the
Reidemeister numbers are always infinite for injective endomorphisms of
Baumslag-Solitar groups.
