How to correctly remove event listener

if i add an event listener like this:

contact.addEventListener(MouseEvent.ROLL_OVER, overMain, false, 0, true);

do i need to remove it like this:

** contact.removeEventListener(MouseEvent.ROLL_OVER, overMain, false);**

or like this:

** contact.removeEventListener(MouseEvent.ROLL_OVER, overMain);**