theorem Th2:
  for I be set, C be Subset of I holds C* c= I*
proof
  let I be set, C be Subset of I;
  thus C* c= I*
  proof
    let a be object;
    assume a in C*;
    then reconsider p = a as FinSequence of C by FINSEQ_1:def 11;
    rng p c= I by XBOOLE_1:1;
    then p is FinSequence of I by FINSEQ_1:def 4;
    hence thesis by FINSEQ_1:def 11;
  end;
end;
