  We study the scattering of a light particle on a bound pair of heavy
particles (e.g., the deuteron) within the fixed center approximation in the
case of light-heavy attraction, solving the integral equation for the
three-body Green's function both in the coordinate and in the momentum space.
The results for the three-body scattering amplitude appear to be ambiguous --
they depend on a single real parameter. This parameter may be fixed by a
three-body input, e.g., the three-body scattering length. We also solve the
integral equation for the three-body Green function in the momentum space,
introducing a finite cut-off. We show that all three approaches are equivalent.
We also discuss how our approach to the problem matches with the introduction
of three-body contact interaction as done by other authors.
