def norm_ref_entry_code(_ordinal, idents, _ids, _standard, datefn, _bib)
        ret = (idents[:metanorma] || idents[:ordinal] || idents[:sdo]).to_s
        /^\[.+\]$/.match?(ret) or ret = "[#{ret}]"
        ret += datefn
        ret.empty? and return ret