The problem of multiuser detection in wireless communications systems adopts,in flat-fading channels, a blind source separation (BSS) formulation ofinstantaneous linear mixtures. This contribution addresses the closed-formsolutions to BSS in the complex-mixture scenario. The algebraic devices whichspan a unifying framework for the complex BSS closed-form estimators aredeveloped. With the aid of these tools, results originally encountered in thereal-mixture case are extended to the complex case, thus highlighting theremarkable parallelism existing between the real and complex problems in thecontext of their analytic solutions. Computer simulations illustrate thetheoretical results and compare the proposed methods to other BSS procedures.