let E be set ; :: thesis: for A being Subset of holds (A * ) * = A *
let A be Subset of ; :: thesis: (A * ) * = A *
( (A * ) * c= A * & A * c= (A * ) * ) by Th44, Th61;
hence (A * ) * = A * by XBOOLE_0:def 10; :: thesis: verum