1. F.L. Wang, M.J. Li, and Z.F. Huang: Guangdong Agricultural Sciences. Vol. 11(2009), p.141. In Chinese.
2. X.L. Chen, S.J. Li, and P.M. Pu: Journal of lake Sciences,. Vol. 18(2006), p.218. In Chinese.
3. L.J. He, J. Gong, C. C, Lai: Industrial Safety and Environmental. Vol. 34(2008), p.23. In Chinese.
4. J.X. Peng, H.J. Cheng: BeiJing: China Environmental Science Press(1988). p.64. In Chinese.
5. E. Sersen, G. Cik, Havranek E: Fresenius Environmental Bulletin. Vol. 14(2005), p.13.