1. Brown, A. L., Wyatt, F. A. and Newton, J. D., Effects of cultivation and cropping on the chemical composition of some western Canada prairie soils. Part II. Sci. Agr.23, 229 (1942).
2. Caldwell, A. C., Wyatt, F. A. and Newton, J. D., Effects of cultivation and cropping on the chemical composition of some western Canada prairie soils. Sci. Agr.19, 258 (1939).
3. Ching-Kwei-Lee and Bray, R. H., Organic matter and nitrogen contents of soils as influenced by management. Soil Sci.68, 203 (1949).
4. Enders, C. und Theis, K., Die Melanoidine und ihre Beziehung zu den Huminsäuren. Brennstoff-Chem.19, 360, 402, 439 (1938).
5. Enders, C., Zur Kenntniss der Melanoidine. Kolloid-Z.85, 74 (1938).