Constraint on the Isgur-Wise function for \bar B --> D semileptonic   decays
  A current algebra sum rule for inclusive decays \bar B --> D + X + \ell + \bar \nu by Bjorken et al. is used to obtain constraints on the Isgur-Wise function \xi(\omega) for \bar B --> D \ell \bar \nu decays. 
Antonio O. Bouzas, Virendra Gupta