1. Asano, G. (1964) Mode of occurrence and microscopic structures of the so-called “Matsuiwa” (a silicified wood). Journal of Mining Institute of Kyushu, 32, 181-201 (in Japanese).
2. Asano, G. and Yui, S. (1962) Pyritic coal balls from Oyake 5-shaku seam of Omine colliery, Chikuho coal field, and a consideration on the original plant debris of the coal. Mining Geology, 12, 143-150 (in Japanese).
3. Endo, Y., Katada, M. and Sasaki, A. (1973) Pyrite in the Permian Toyoma Formation of the southern Kitakami mountains, Japan. Bulletin of Geological Survey of Japan, 24, 113-121 (in Japanese).
4. Canfield, D.E. and Raisewell, R. (1991) Pyrite formation and fossil preservation. In Taphonomy: Releasing the data locked in the fossil record. (Allison, P.A and Briggs, D.E.G. Eds.). Volume 9 of Topic in Geobiology, Plenum Press, New York, 337-387.
5. Sulfur isotopic variations in low-sulfur coals from the Rocky Mountain region