1. Distribution of micronutrients in Ibadan soils;Ali,1978
2. Cr, Cd, As, Se, Hg and aquatic life—a brief literature review;Anonymous,1971
3. Sampling and storage of natural waters for trace metal analysis;Bartley;Water Res.,1977
4. Trace Elements in Biochemistry;Bowen,1966
5. Heavy metals as contaminants of the human environment;Bryce-Smith,1975