1. 1) Japan Coast Guard, “Japan Coast Guard Annual Report 2012,” Nikkei Printing Inc., Tokyo (2012), p. 80.
2. 2) Yamasaki, Y., Sugiyama, M., Jpn. J. Forensic Sci. Tech., 11, (2), 139 (2006).
3. 3) Takasuga, T, Kankyou Jouka Gijutsu, 2, (2), 10 (2003).
4. 4) Rubber-Determination of free sulfur, JIS K 6234.
5. 5) Nagai, M., Ind. Eng. Chem., Prod. Res. Dev., 24, 489 (1985).