protected function _prepareReference(Zend_Db_Table_Abstract $dependentTable, Zend_Db_Table_Abstract $parentTable, $ruleKey)
    {
        $parentTableName = (get_class($parentTable) === 'Zend_Db_Table') ? $parentTable->getDefinitionConfigName() : get_class($parentTable);
        $map = $dependentTable->getReference($parentTableName, $ruleKey);

        if (!isset($map[Zend_Db_Table_Abstract::REF_COLUMNS])) {
            $parentInfo = $parentTable->info();
            $map[Zend_Db_Table_Abstract::REF_COLUMNS] = array_values((array) $parentInfo['primary']);
        }

        $map[Zend_Db_Table_Abstract::COLUMNS] = (array) $map[Zend_Db_Table_Abstract::COLUMNS];
        $map[Zend_Db_Table_Abstract::REF_COLUMNS] = (array) $map[Zend_Db_Table_Abstract::REF_COLUMNS];

        return $map;
    }