  In this paper we complete the classification of effective C*-actions on
smooth affine surfaces up to conjugation in the full automorphism group and up
to inversion of C*. If a smooth affine surface V admits more than one C*-action
then it is known to be Gizatullin i.e., it can be completed by a linear chain
of smooth rational curves. In our previous paper we gave a sufficient
condition, in terms of the Dolgachev- Pinkham-Demazure (or DPD) presentation,
for the uniqueness of a C*-action on a Gizatullin surface. In the present paper
we show that this condition is also necessary, at least in the smooth case. In
fact, if the uniqueness fails for a smooth Gizatullin surface V which is
neither toric nor Danilov-Gizatullin, then V admits a continuous family of
pairwise non-conjugated C*-actions depending on one or two parameters. We give
an explicit description of all such surfaces and their C*-actions in terms of
DPD presentations. We also show that for every k > 0 one can find a Danilov-
Gizatullin surface V (n) of index n = n(k) with a family of pairwise
non-conjugate C+-actions depending on k parameters.
