An estimate of the QCD corrections to the decay Z --> W u d
  We present an estimate of perturbative QCD corrections to the decay $Z \to Wu\bar d$. A simple approximate approach is described in detail. The difference of masses of $M_Z$ and $M_W$ is used as an expansion parameter. A complete analytical formula for a part of the corrections is also presented. 
Andrzej Czarnecki and Kirill Melnikov