theorem Th77:
  for E be Enumeration of {x} holds E = <*x*>
proof
  let E be Enumeration of {x};
A1: len E=card {x} =1 by CARD_1:def 7;
  then 1 in dom E by FINSEQ_3:25;
  then E.1 in rng E by FUNCT_1:def 3;
  then E.1=x by TARSKI:def 1;
  hence thesis by A1,FINSEQ_1:40;
end;
