Heavy-quark symmetries in the light of nonperturbative QCD approaches
  We critically review the validity of heavy-quark spin and flavor symmetries in heavy-light decay constants, form factors and effective couplings obtained within a nonperturbative framework, the ingredients of which are all motivated by Dyson-Schwinger equations studies of QCD. Along the way, we make new predictions for two effective nonphysical couplings: g_{DsDK} = 24.1+2.5/-1.6 and g_{BsBK} = 33.3+4.0/-3.7. 
Bruno El-Bennich, Craig D. Roberts and Mikhail A. Ivanov
nucl-th hep-ex hep-lat hep-ph nucl-ex