Phenomenological Bounds on B to Light Semileptonic Form Factors
  The form factors for the weak currents between B and light mesons are studied by relating them to the corresponding D form factors at q^2_{max} according to HQET, by evaluating them at q^2=0 by QCD sum rules, and by assuming a polar q^2 dependence. The results found are consistent with the information obtained from exclusive non-leptonic two-body decays and, with the only exception of A_1, with lattice calculations. 
D. Falcone, P. Santorelli, N. Tancredi, F. Tramontano