The four volumes of "Iwao OYAMA" written by Noboru KOJIMA (published by Bungeishunju Ltd., later Bunshun Bunko) is a representative biography, but now is out of stock.
代表的な伝記として、児島襄著『大山巌』全４巻（文藝春秋のち文春文庫）があるが品切れ。