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: 
          ! Calculate the generation probability of a given excitation for the
          ! Hubbard model in momentum space.  The Hubbard model is a special case
          ! as it is a one-band system and so the generation probability is
          ! independent of the virtual spin-orbitals into which electrons are
          ! excited and depends only upon the spin-orbitals from which we excite.
          !
  