IIA of that reference), using similar arguments at the quark level as in Eq. , that in the heavy sector the coupling of the light vectors to the charmed mesons leaves the heavy quark as a spectator. Then one can map the matrix elements with light quarks to the equivalent ones in $\textrm{SU(3)}$, with the result that using Eq.  in $\textrm{SU(4)}$, with the matrices of Eqs.  and , the result obtained is the same as using this quark model with the heavy quarks as spectators. In other words, one is making use of the $\textrm{SU(3)}$ content of $\textrm{SU(4)}$. Furthermore, the fact that the heavy quarks are spectators has immediately as a consequence that the interaction complies with the rules of heavy quark spin symmetry (HQSS). However, if we have non diagonal transitions like $\Xi_c \bar{K}\to \Xi D$ one must exchange a $D^*_s$ and the heavy quarks are involved. Here $\textrm{SU(4)}$ is used and the result is more model dependent, apart from not satisfying the rules of HQSS. However, in this case HQSS should not be satisfied, because the heavy quark propagator goes as $(1/m_{D^*_s})^2$ and those terms are subleading in the $(1/m_Q)$ counting ($m_Q$ is the mass of the heavy 