Impact of the W boson decay width on photon bremsstrahlung accompanying   W pair production
  The bremsstrahlung spectrum of photons accompanying $W$ pair production depends on the decay width of the unstable $W$ bosons. The dependence arises from the interference between emission at different stages of the production and decay process. We present a quantitative discussion of this effect, and consider the implications for measurements at LEP2 and LC energies. 
A.P. Chapovsky, V.A. Khoze, W.J. Stirling (Durham)