  We compute several total and differential cross sections relevant to top and
WWZ physics at future $e^+e^-$ colliders taking into account the full set of
Feynman diagrams for six fermion final states. We also include in our
calculations initial state radiation and beamstrahlung effects, and the most
important QCD corrections in an approximate (naive) form. We compare such a
complete approach with "production x decay" approximation and we suggest that
in many physical studies the former is needed.
