1. L. N. Aleksandrova, Soil Organic Matter and Its Transformation (Nauka, Leningrad, 1980) [in Russian].
2. S. N. Aleshin, L. K. Shevtsova, and V. A. Chernikov, “Changes in Soil Organic Matter under Long-Term Fertilization Conditions,” Agrokhimiya, No. 6, 49–54 (1971).
3. N. P. Bityutskii, “Methods of Regulating the Iron Nutrition of Plants,” Agrokhimiya, No. 3, 98–105 (1994).
4. H. Bekker et al., Organikum: organisch-chemisches Grundpraktikum (Deutscher Verlag, Berlin, 1964).
5. L. J. Bellamy, The Infra-Red Spectra of Complex Molecules (Methuen, London, 1959).