  We derive a generalization of the flat space Yang's and Newman's equations
for self-dual Yang-Mills fields to (locally) conformally Kahler Riemannian
4-manifolds. The results also apply to Einstein metrics (whose full curvature
is not necessarily self-dual). We analyse the possibility of hidden symmetries
in the form of Backlund transformations, and we find a continuous group of
hidden symmetries only for the case in which the geometry is conformally
half-flat. No isometries are assumed.
