protected static function get_fields()
 {
     return implode(', ', array(self::select_fields(), UserProfile::select_fields(), User::select_fields('referer'), ACLGroup::select_fields(), Country::select_fields()));
 }
 protected static function get_fields()
 {
     return self::select_fields() . ', ' . ACLGroup::select_fields() . ', ' . ACL::select_fields();
 }