1. 1. “Quality Standard for Tap Water (in Japanese)”, Ministry of Health, Labour and Welfare of Japan, http://www.mhlw.go.jp/stf/seisakunitsuite/bunya/topics/bukyoku/kenkou/suido/kijun/index.html, accessed 20 July 2016.
2. 2. “Guidelines for Drinking-water Quality”, 4th ed., 2011, World Health Organization, Geneva.
3. 3. ISO Guide 34:2009, “General Requirements for the Competence of Reference Material Producers”, International Standards Organization, Geneva.
4. 4. K. Inagaki, A. Takatsu, T. Kuroiwa, A. Nakama, S. Eyama, K. Chiba, and K. Okamoto, Anal. Bioanal. Chem., 2004, 378, 1271.
5. 5. K. Inagaki, A. Takatsu, T. Watanabe, Y. Aoyagi, T. Yarita, K. Okamoto, and K. Chiba, Anal. Bioanal. Chem., 2007, 387, 2325.