public static function validateExternalRaterCode($a_ref_id, $a_code)
 {
     if (!isset($_SESSION["360_extrtr"][$a_ref_id])) {
         $svy = new self($a_ref_id);
         $svy->loadFromDB();
         if ($svy->canStartSurvey(null, true) && $svy->get360Mode() && $svy->isAnonymousKey($a_code)) {
             $anonymous_id = $svy->getAnonymousIdByCode($a_code);
             if ($anonymous_id) {
                 if (sizeof($svy->getAppraiseesToRate(null, $anonymous_id))) {
                     $_SESSION["360_extrtr"][$a_ref_id] = true;
                     return true;
                 }
             }
         }
         $_SESSION["360_extrtr"][$a_ref_id] = false;
         return false;
     }
     return $_SESSION["360_extrtr"][$a_ref_id];
 }