Resummed corrections to the \rho parameter in the complex mass scheme
  We present all order results for the heavy top corrections to the \rho parameter in the complex mass scheme. We derive translation formulas between the complex mass and the on-shell scheme and show that they are ultimately equivalent. We show that a naive treatment with a fixed width for the top quark cannot give even approximately correct results. 
D. Bettinelli, J. J. van der Bij
hep-ph