theorem Th22:
  for D being set, D1 being Subset of D for p being FinSequence of D1
  holds p is FinSequence of D
proof
  let D be set, D1 be Subset of D;
  let p be FinSequence of D1;
  rng p c= D1 by FINSEQ_1:def 4;
  hence rng p c= D by XBOOLE_1:1;
end;
