Renormalons and Power Corrections
  Even for short-distance dominated observables the QCD perturbation expansion is never complete. The divergence of the expansion through infrared renormalons provides formal evidence of this fact. In this article we review how this apparent failure can be turned into a useful tool to investigate power corrections to hard processes in QCD. 
M. Beneke (Aachen) and V.M. Braun (Regensburg)