EXCALIBUR -- a Monte Carlo program to evaluate all four fermion   processes at LEP 200 and beyond
  A Monte Carlo program is presented that computes all four fermion processes in $e^+ e^-$ annihilation. QED initial state corrections and QCD contributions are included. Fermions are taken to be massless, allowing a very fast evaluation of the matrix element. A systematic, modular and self-optimizing strategy has been adopted for the Monte Carlo integration, that serves also as an example for further event generators in high energy particle physics. 
F. Berends, R, Kleiss and R. Pittau