Exact Duality and Bjorken Sum Rule in Heavy Quark Models \`a la   Bakamjian-Thomas
  The heavy mass limit of quark models based on the Bakamjian-Thomas cons\-truction reveals remarkable features. In addition to previously demonstrated properties of covariance and Isgur-Wise scaling, exact duality, leading to the Bjorken-Isgur-Wise sum rule, is proven, for the first time to our knowledge in relativistic quark models. Inelastic as well as elastic contributions to the sum rule are then discussed in terms of ground state averages of a few number of operators corresponding to the nonrelativistic dipole operator and various relativistic corrections. 
A. Le Yaouanc, L. Oliver, O. P\`ene and J.-C. Raynal