“…There is a wide spectrum of nonrelativistic and relativistic quark models, see e.g. [1,4,5,[12][13][14] for reviews, including quark models based on one-gluon exchange [11,15,16], Goldstone-boson exchange [17,18], diquark models [19][20][21], string models [22], large-N c models [23,24], hypercentral quark models [25,26], light-front and holographic models [27], and models based on Bethe-Salpeter equations [28,29].…”