Instantaneous Bethe-Salpeter Equation: (Semi-)Analytical Solution
  The Bethe-Salpeter equation for bound states of a fermion-antifermion pair in the instantaneous approximation for the involved interaction kernel is converted into an equivalent matrix eigenvalue problem with explicitly (algebraically) given matrices. 
Wolfgang Lucha, Khin Maung Maung, F. F. Schoberl