1. Origins and Distribution of Nitrogen in Soil;Stevenson,1965
2. Humus Chemistry, Genesis, Composition, Reactions;Stevenson,1982
3. Soil Organic Carbon, Nitrogen and Fertility;Campbell,1978
4. Carbohydrates;Lowe,1978
5. Organic Nitrogen, Phosphorus and Sulphur in Soils;Kowalenko,1978