_pdbx_nmr_chem_shift_reference.carbon_shifts_flag       ? 
    _pdbx_nmr_chem_shift_reference.details                  "External DSS sample" 
    _pdbx_nmr_chem_shift_reference.entry_id                 1ABC
    _pdbx_nmr_chem_shift_reference.id                       1 
    _pdbx_nmr_chem_shift_reference.label                    chemical_shift_reference_