  An S-Matrix ansatz is used to determine the mass and width of the Z boson, as
well as the contributions of gamma/Z interference and Z boson exchange to
fermion-pair production. For this purpose we use hadron and lepton-pair
production cross sections and lepton forward-backward asymmetries that have
been measured with the L3 detector at centre-of-mass energies between 87GeV and
189GeV.
