Reduction of the instantaneous Bethe-Salpeter equation for q-q bound states

We present a straightforward method to reduce the instantaneous Bethe-Salpeter equation to a set of coupled equations for radial wave functions. In the case of positronium, in particular, the results obtained by Cung {ital et} {ital al}. follow immediately; our procedure is, however, much more general and is intended to be applied to mesonic bound states where competing models need to be tested. We also briefly comment on the numerical solution of the ensuing equations.