reserve E for non empty set;
reserve a for Element of E;
reserve A, B for Subset of E;
reserve Y for set;
reserve p for FinSequence;
reserve e, e1, e2 for Singleton of E;

theorem
  ex p st p is FinSequence of E & rng p = e & len p = 1
proof
  consider a such that
  a in E and
A1: e = {a} by Th6;
  rng <*a*> = {a} & len <*a*> = 1 by FINSEQ_1:39;
  hence thesis by A1;
end;
