reserve E, x, y, X for set;
reserve A, B, C for Subset of E^omega;
reserve a, b for Element of E^omega;
reserve i, k, l, kl, m, n, mn for Nat;

theorem
  (A |^ k)? c= A*
proof
  (A |^ k)? = (A |^ k) |^ (0, 1) by Th79;
  hence thesis by Th69;
end;
