  In a previous work \cite{mbeleka}, we have modelled the rotation curves (RC)
of spiral galaxies by including in the equation of motion dynamical terms from
an external real self-interacting scalar field, $\phi$, minimally coupled to
gravity and which respects the equivalence principle in the absence of
electromagnetic fields. This model appears to have three free parameters : the
turnover radius, $r_{0}$, the maximum rotational velocity, $v_{max} =
v(r_{0})$, plus a strictly positive integer, $n$. Here, the coupling of the
$\phi$-field to other kinds of matter is emphasized at the expense of its
self-interaction. This reformulation presents the very advantageous possibility
that the same potential may be used now for all galaxies. New correlations are
established.
