代表的な2社のもう1社は? https://rio.st/2008/05/26/%e4%bb%a3%e8%a1%a8%e7%9a%84%e3%81%aa2%e7%a4%be%e3%81%ae%e3%82%82%e3%81%861%e7%a4%be%e3%81%af%ef%bc%9f/