Four-loop moments of the heavy quark vacuum polarization function in   perturbative QCD
  New results at four-loop order in perturbative QCD for the first two Taylor coefficients of the heavy quark vacuum polarization function are presented. They can be used to perform a precise determination of the charm- and bottom-quark mass. Implications for the value of the quark masses are briefly discussed. 
K. G. Chetyrkin, J. H. K\"uhn and C. Sturm