Single Scale Tadpoles and O(GF mt^2 as^3) Corrections to the rho   Parameter
  We present a new set of high precision numerical values of four-loop single-scale vacuum integrals, which we subsequently use to obtain the non-singlet corrections to the rho parameter at O(GF mt^2 as^3). Our result for Delta rho is in agreement with the recent calculation [1]. 
R. Boughezal, M. Czakon