Two Loop Electroweak Bosonic Corrections to the Muon Decay Lifetime
  A review of the calculation of the two loop bosonic corrections to $\Delta r$ is presented. Factorization and matching onto the Fermi model are discussed. An approximate formula, describing the quantity over the interesting range of Higgs boson mass values from 100 GeV to 1 TeV is given. 
M. Awramik and M. Czakon