1. Japan Sewage Works Association (1974) Gesui Shiken Hōhō, p 132
2. Japanese Standards Association (1974) Testing Methods for Industrial Waste Water, p 86. (Japanese Industrial Standards Committee)
3. American Public Health Association/American Water Works Association/Water Pollution Control Federation (1975) Standard Methods for the Examination of Water and Waste Water, 14th edit, p 466
4. Ichinose N (1978) Japan Analyst 27:671
5. Ichinose N, Shimizu C, Kurokura H, Inui T, Kadohata K (1982) Japan Analyst (Bunseki Kagaku) 31:532