1. A survey of nitrogen levels in the major soils of Ghana;Asamoa,1980
2. Total nitrogen;Bremner,1965
3. Methods of analysis for soils, plants and water;Chapman,1961
4. Distribution and cycling of nitrogen, phosphorus, potassium and calcium in a secondary-growth Douglas-fir ecosystem;Cole,1968
5. Weather information from the University of Ife, Ile-Ife;Duncan,1974