anchor.diff:          ! fortran numbers bits from 0...
           type(basis_fn_t), allocatable :: basis_fns(:) ! (nbasis)
   
  -        ! number of basis functions.
  -        ! For the Hubbard model is equal to twice the number of sites as there are
  +        ! Number of basis functions.
  +        ! For the Hubbard model this is equal to twice the number of sites as there are
           ! 2 spin orbitals per site, for the Heisenberg model to the number of sites,
           ! for UEG equal to twice the number of k-points within the energy cutoff and for
           ! read in (e.g. molecular) systems the number of single-particle states read in.
  
positive.code:         ! strings separately, and so basis_length is 2*ceiling(nbasis/(2*i0_length)).
          integer :: basis_length
  
          ! DMQMC uses two determinants for each psip to refer to the two components
          ! of the relevant matrix element. Hence, the bitstring which is stored in DMQMC has
          ! 2*basis_length components. There are some procedures which required basis_length
          ! when used for stahndard FCIQMC but 2*basis_length when used for DMQMC. It is
          ! therefore useful to have a quantity which equal to 2*basis_length for DMQMC and
          ! equal to basis_length for other methods. Then a procedure can use this quantity
          ! and will work for both methods, making it general. This quantity is total_basis_length.
  
negative.code:         !     units of the lattice vectors of the primitive unit cell.
          ! Obviously we should not convert between descriptions within one
          ! calculation! ;-)
          ! For molecular systems l is not used and remains deallocated.
          integer, allocatable :: l(:)
          integer :: spatial_index
          ! Index of the irreducible representation spanned by the orbital.  Used only
  