reserve E, x, y, X for set;
reserve A, B, C, D for Subset of E^omega;
reserve a, a1, a2, b, c, c1, c2, d, ab, bc for Element of E^omega;
reserve e for Element of E;
reserve i, j, k, l, n, n1, n2, m for Nat;

theorem Th62:
  (A*)* = A*
proof
  (A*)* c= A* & A* c= (A*)* by Th43,Th60;
  hence thesis by XBOOLE_0:def 10;
end;
