ZFITTER -- An Analytical Program for Fermion Pair Production in e+e-   Annihilation
  We describe how to use ZFITTER, a program based on a semi-analytical approach to fermion pair production in e+e- annihilation and Bhabha scattering. A flexible treatment of complete ${\cal O}(\alpha)$ QED corrections, also including higher orders, allows for three calculational {\bf chains} with different realistic sets of restrictions in the photon phase space. {\tt ZFITTER} consists of several {\bf branches} with varying assumptions on the underlying hard scattering process. One includes complete ${\cal O}(\alpha)$ weak loop corrections with a resummation of leading higher-order terms. Alternatively, an ansatz inspired from S-matrix theory, or several model-independent effective Born cross sections may be convoluted. The program calculates cross sections, forward-backward asymmetries, and for $\tau$~pair production also the final-state polarization. Various {\bf interfaces} allow fits to be performed with different sets of free parameters. 
D. Bardin, M. Bilenky, A. Chizhov, O. Fedorenko, S. Ganguli, A. Gurtu,   M. Lokajicek, G. Mitselmakher, A. Olshevsky, J. Rid...