1. K. Nagayama, The Connoisseurs Book of Japanese Swords, Kodansha International (1997).
2. L. Kapp, The Craft of the Japanese Sword, Kodansha International (1998).
3. M. Chkashige, Oriental Alchemy, Samuel Weiser press (1974).
4. M. R. Notis, Mat. Char. Vol. 45 (2000), p.253.
5. T. Inoue, Mat. Sci. Res. Int. Vol. 3 (1997), p.193.