The first appearance in "Azuma Kagami" (The Mirror of the East) is the article dated April 23, 1184, and Masayoshi SHIMOKOBE made a request through Toshikane, and Toshikane wrote gosho (writings/letters of superior) for mokudai (deputy kokushi, or a deputy provincial governor) by order of Yoritomo.
『吾妻鏡』での初出は1184年（元暦元年）4月23日条で、下河辺政義が俊兼を通じて訴え出、頼朝の命により、俊兼が常陸国目代に御書を代書している。