  Nucleon structure functions, as measured in deep-inelastic lepton scattering,
are studied within a covariant scalar diquark spectator model. Regarding the
nucleon as an approximate two-body bound state of a quark and diquark, the
Bethe-Salpeter equation (BSE) for the bound state vertex function is solved in
the ladder approximation. The valence quark distribution is discussed in terms
of the solutions of the BSE.
