anchor.diff:          call choose_ab_hub_k(cdet%f, cdet%unocc_list_alpha, ij_sym, connection%to_orb(1), connection%to_orb(2))
   
           ! 3. Calculate the generation probability of the excitation.
  -        ! For two-band systems this depends only upon the orbitals excited from.
  +        ! For one-band systems this depends only upon the orbitals excited from.
           pgen = calc_pgen_hub_k(ij_sym, cdet%f, cdet%unocc_list_alpha)
   
           ! 4. find the connecting matrix element.
  
positive.code:                                  connection%from_orb(1), connection%from_orb(2), ij_sym)
  
          ! 2. Calculate the generation probability of the excitation.
          ! For two-band systems this depends only upon the orbitals excited from.
          pgen = calc_pgen_hub_k(ij_sym, cdet%f, cdet%unocc_list_alpha)
  
          ! The hubbard model in momentum space is a special case. Connected
  
negative.code:         !   \Gamma_i* x \Gamma_i = 1
          ! and direct products in Abelian groups commute, it follows that:
          !   \Gamma_b = \Gamma_i x \Gamma_j x \Gamma_a*
          ! Thus k_b is defined by i,j and a.  As we only consider one-band
          ! systems, b is thus defined by spin conservation.
  
          ! One electron must be in unocc_list_alpha, so we can use the
  