private function getOverDriveMetaData()
 {
     if ($this->overDriveMetaData == null) {
         require_once ROOT_DIR . '/sys/OverDrive/OverDriveAPIProductMetaData.php';
         $this->overDriveMetaData = new OverDriveAPIProductMetaData();
         $this->overDriveMetaData->productId = $this->overDriveProduct->id;
         $this->overDriveMetaData->find(true);
     }
     return $this->overDriveMetaData;
 }
 private function getOverDriveCover($id = null)
 {
     require_once ROOT_DIR . '/sys/OverDrive/OverDriveAPIProduct.php';
     require_once ROOT_DIR . '/sys/OverDrive/OverDriveAPIProductMetaData.php';
     $overDriveProduct = new OverDriveAPIProduct();
     $overDriveProduct->overdriveId = $id == null ? $this->id : $id;
     if ($overDriveProduct->find(true)) {
         $overDriveMetadata = new OverDriveAPIProductMetaData();
         $overDriveMetadata->productId = $overDriveProduct->id;
         $overDriveMetadata->find(true);
         $filename = $overDriveMetadata->cover;
         if ($filename != null) {
             return $this->processImageURL($filename);
         } else {
             return false;
         }
     } else {
         return false;
     }
 }