1. P. G. Akulov, Recovery of Fertility and Productivity of Chernozem (Kolos, Moscow, 1992) [in Russian].
2. V. V. Dokuchaev, “Russian chernozem,” in Selected Works (Gossel’khozizdat, Moscow, 1948), Vol. 1. [in Russian]
3. N. E. Zav’yalov, “Methodological approaches to the study of humus status of arable soils,” Plodorodie, No. 1, 11–15 (2006).
4. A. L. Ivanov, V. G. Sychev, L. M. Derzhavin, et al., Agrobiochemical Cycle of Phosphorus (Rossel’khozakademiya, Moscow, 2012) [in Russian].
5. A. N. Kashtanov and V. E. Yavtushenko, Agroecology of Slope Soils (Kolos, Moscow, 1997) [in Russian].