( 3 ) the derived set of - limit set is equal to the derived set of the set of the recurrent points ( 3 ) -极限集的导集等于回复点集的导集。
2.
( 4 ) the two - order derived set of non - wandering set is equal to the two - order derived set of the set of recurrent points ( 4 )非游荡集的二阶导集等于回复点集的二阶导集。