  The semi-relativistic quark potential model is surprisingly powerful for
heavy-light systems if the bound state equation is treated correctly using
1/m_Q expansion with heavy quark mass m_Q. We elucidate the reasons why our
semi-relativistic model succeeds in predicting and reproducing all the mass
spectra of heavy-light systems so far reported, D/D_s/B/B_s, by reviewing and
comparing recent experimental data with the results of our model and others.
Especially the mass spectra of the so-called D_{sJ}, i.e., D_{s0}^* and
D_{s1}', are successfully reproduced only by our model but not by other models.
