private function buildHtmlHeadEntrySet(array $component_ids, $mode)
    {
        $set = new SwatHtmlHeadEntrySet();

        foreach ($component_ids as $component_id) {
            $set->addEntrySet(
                self::$components[$component_id]->getHtmlHeadEntrySet($mode)
            );
        }

        $set->addEntry($this->getAttributionHtmlHeadEntry());

        return $set;
    }