The Quark Structure of Light Mesons
  We present the results of a covariant constituent quark model, based on the Bethe-Salpeter equation, where confinement is implemented by a string like linear potential explaining the Regge trajectories. An instanton induced quark force explains not only the splitting and mixing of pseudoscalar mesons, but suggest that such effects are also present in the scalar spectrum and in a violation of the OZI rule in the decays of scalar particles into pseudoscalars. We demonstrate that a covariant treatment that takes into account the relativistic components in the amplitudes is of utmost importance when describing properties of deeply bound states and/or processes at higher momentum transfer. 
B.C. Metsch, H.R. Petry