Microscopic derivation of the pion coupling to heavy-light mesons
  The Goldberger--Treiman relation for heavy--light systems is derived in the context of a quark model. As a paradigmatic example, the case of ${\bar D}\to {\bar D}' \pi $ is studied in detail. The fundamental role played by the pion two-component wave function, in the context of the Salpeter equation, is emphasized. 
A.V. Nefediev, J.E.F.T. Ribeiro and Adam P. Szczepaniak