Miller index h of a reflection. The values of
               the Miller indices in the DIFFRN_REFLN category need not match
               the values of the Miller indices in the REFLN category if a
               transformation of the original measured cell has taken place.
               Details of the cell transformation are given in
               _diffrn_reflns.reduction_process. See also
               _diffrn_reflns.transf_matrix[][].