Duality-Violating 1/m_Q Effects in Heavy Quark Decay
  I identify a source of \Lambda_{QCD}/m_Q corrections to the assumption of quark-hadron duality in the application of heavy quark methods to inclusive heavy quark decays. These corrections could substantially affect the accuracy of such methods in practical applications and in particular compromise their utility for the extraction of the Cabibbo-Kobayashi-Maskawa matrix element V_{cb}. 
Nathan Isgur