reserve A,B,C for Ordinal;
reserve a,b,c,d for natural Ordinal;
reserve l,m,n for natural Ordinal;

theorem Th9:
  n divides {} & 1 divides n
proof
  {} = n *^ {} by ORDINAL2:35;
  hence n divides {};
  n = 1 *^ n by ORDINAL2:39;
  hence thesis;
end;
