1. Analysis Method of Water and Waste Mater, Beijing (China): Chinese Environment Protection Agency, 1989.
2. Xiong, C., Zhu, T., and Zhang, J., Yejin Fenxi, 1993, vol. 13, no.3, p. 30.
3. Fujita, Y., Mori, I., Toyoda, M., and Matsuo, T., Anal. Sci., 1993, vol. 9, p. 829.
4. Koh, T. and Sugimoto, T., Anal. Chim. Acta, 1996, vol. 333, p. 167.
5. Singh, H.B., Kumar, B., and Sharma, R.L., Analyst, 1989, vol. 114, p. 853.