theorem
  <*x*> is NonatomicND of {1},{x}
  proof
    take <*NDSS({1},{x})*>;
    thus <*NDSS({1},{x})*> IsNDRankSeq {1},{x} by Th27;
    <*x*> in NDSS({1},{x})
    proof
      1 in {1} & x in {x} by TARSKI:def 1;
      then <*x*> is Relation of {1},{x} by RELSET_1:3;
      hence thesis;
    end;
    hence thesis by FINSEQ_3:135;
  end;
