I am honored to be or have been personal friends with the authors of these very important books, whom I have relied upon heavily in writing my own books, including Ryoma.

坂本龍馬全集,中岡慎太郎全集, 坂本龍馬写真集（宮地佐一郎）

定本坂本龍馬伝 (松岡司)

坂本龍馬大鑑 (小美濃清明)

Thank you Mr. Miyaji, Mr. Matsuoka, Mr. Omino.