1. S. Waldman, Newsweek, July 15, 1991.
2. M. A. Jandreski, Clinical Chem. News, January 1994.
3. A. P. Morton, S. Partridge, A. Blair, Chem. In Britain, October 1985, p. 923.
4. R. D. Field, Clinical Chem. News, October 1992.
5. C. W. Randall, C. D. Donaldson, P. J. Wigington, Jr., T. J. Grizzard, W. R. Knocke, Water Sci. TechnoL, 1985, 17, 1461.