public static function getAvailablePortfolioLinksForUserIds(array $a_owner_ids, $a_back_url = null)
 {
     $res = array();
     include_once "Modules/Portfolio/classes/class.ilPortfolioAccessHandler.php";
     $access_handler = new ilPortfolioAccessHandler();
     $params = null;
     if ($a_back_url) {
         $params = array("back_url" => rawurlencode($a_back_url));
     }
     include_once "Services/Link/classes/class.ilLink.php";
     foreach ($access_handler->getShardObjectsDataForUserIds($a_owner_ids) as $owner_id => $items) {
         foreach ($items as $id => $title) {
             $url = ilLink::_getLink($id, 'prtf', $params);
             $res[$owner_id][$url] = $title;
         }
     }
     return $res;
 }