theorem Th35:
  { w } is AntiChain_of_Prefixes-like
proof
  thus for x st x in { w } holds x is FinSequence by TARSKI:def 1;
  let p1,p2;
  assume that
A1: p1 in { w } and
A2: p2 in { w };
 p1 = w by A1,TARSKI:def 1;
  hence thesis by A2,TARSKI:def 1;
end;
