1. ACC/SCN, Fifth report on the world nutrition situation, Geneva: United Nations, Administrative Committee on Coordination/Sub-Committee on Nutrition (2004).
2. WHO, The World Health Report, Geneva WHO (2002).
3. Marschner H, San Diego: Academic Press, (1995).
4. Mori S, Curr Opin Plant Biol, 2 (1999) 250.
5. Takagi S, Soil Sci Plant Nutr, 22 (1976) 423.