public function createFolder($folderName, $folderResourceId = null)
    {
        $category = new Zend_Gdata_App_Extension_Category(
            self::DOCUMENTS_CATEGORY_TERM,
            self::DOCUMENTS_CATEGORY_SCHEMA
        );
        $title    = new Zend_Gdata_App_Extension_Title($folderName);
        $entry    = new Zend_Gdata_Entry();

        $entry->setCategory(array($category));
        $entry->setTitle($title);

        $uri = self::DOCUMENTS_LIST_FEED_URI;
        if ($folderResourceId != null) {
            $uri = self::DOCUMENTS_FOLDER_FEED_URI . '/' . $folderResourceId;
        }

        return $this->insertEntry($entry, $uri);
    }