Natural Deduction rules for biconditional

When dealing with the biconditional, $⟺$, there is two natural deduction rules, one for introduction and elimination: ?

$$\frac{A\to B,B\to A}{A⟺B}(⟺I)\frac{A⟺B}{(A\to B)\wedge (B\to A)}(⟺E)$$