The effective electroweak mixing angle $\sin^2\theta_{eff}$ with   two-loop bosonic contributions
  We present the results for the full electroweak two-loop bosonic contributions to the effective leptonic mixing angle of the $Z$ boson, $\sin^2\theta_{\rm eff}$, in the Standard Model. A method applied to extract collinear divergences from two-loop vertex-functions is described. Comparisons of our results with those from a recent previous calculation show complete agreement. 
W. Hollik, U. Meier and S. Uccirati