On Instanton Contributions to the tau Hadronic Width
  Comparing the results of finite energy and Borel transformed sum rules for the difference of vector and axial vector current correlators we evaluate the instanton contributions to the $\tau$ hadronic width. In contrast to an explicit theoretical calculation we find that the instanton contributions to the $\tau$ hadronic width are much smaller than the standard nonperturbative corrections. 
V.Kartvelishvili and M.Margvelashvili