株式会社岡山国際サーキットの株式取得(子会社化)についてのお知らせ [We resolved on the acquiation of whole stock in Okayama International Circuit Co., Ltd.] (PDF) (Press release) (in Japanese). Aska Corporation. March 12, 2012. Archived from the original(PDF) on September 21, 2013. Retrieved April 24, 2012.
株式会社岡山国際サーキットの株式取得(子会社化)についてのお知らせ [We resolved on the acquiation of whole stock in Okayama International Circuit Co., Ltd.] (PDF) (Press release) (in Japanese). Aska Corporation. March 12, 2012. Archived from the original(PDF) on September 21, 2013. Retrieved April 24, 2012.