reserve T for non empty RelStr,
  a for Element of T;

theorem
  for R be Relation, a be set st R is Order of {a} holds R = id {a}
proof
  let R be Relation, a be set;
  assume
A1: R is Order of {a};
then A2: R <> {};
  R c= [:{a},{a}:] by A1;
  then R c= {[a,a]} by ZFMISC_1:29;
  then R = { [a,a] } by A2,ZFMISC_1:33;
  hence thesis by SYSREL:13;
end;
