1. AOAC, Official Methods of Analysis of the Association of Official Analytical Chemists, 11th edn. Washington, DC, 1970.
2. in: Water Deficits and Plant Growth, Vol. 5. Ed. by pp. 199–219. Academic Press, New York 1978.
3. The Nigerian Society for Plant Protection. Occasional Publication No. 3, (1980) 88–101