  Achieving self-consistent simultaneous interpretations of pions and kaons as
bound states of quark and antiquark and as the (almost) massless boson states
related, according to Goldstone's theorem, to the dynamical (and explicit)
breakdown of the chiral symmetries of QCD still represents a major challenge.
Applying inversion techniques to conveniently simplified versions of the
homogeneous Bethe-Salpeter equation, governing bound states in quantum field
theory, enables us to get along a straightforward route a qualitative idea of
how the underlying effective interaction might look like.
