public static function fetchByIdentifier( $identifier, $groupID )
    {
        $db = eZDB::instance();
        $identifier = $db->escapeString( $identifier );
        $states = self::fetchByConditions( array( "ezcobj_state.identifier='$identifier'", "ezcobj_state_group.id=$groupID" ), 1, 0 );
        $state = count( $states ) > 0 ? $states[0] : false;
        return $state;
    }