Four-Loop Tadpoles: Applications in QCD
  Recent applications of single-scale four-loop tadpoles are briefly reviewed. An algorithm for the evaluation of current correlators based on differential equations is described and applied to obtain high moments of the vacuum polarization function at O(alphas^2) as a preparation of O(alphas^3) calculations. 
R. Boughezal, M. Czakon, T. Schutzmeier