BRYANT, Anthony J. Early Samurai: 200-1500 AD. [s.l.]: Osprey Publishing, 1991. Dostupné online. S. 65.
RATTI, Oscar; WESTBROOK, Adele. Secrets of the samurai: a survey of the martial arts of feudal Japan. Boston, MA: Tuttle Publishing, 1973. Dostupné online. S. 211.