1. B. F. Aparin, G. A. Kasatkina, N. N. Matinyan, and E. Yu. Sukhacheva, Red Data Soil Book of Leningrad Oblast (Aeroplan, St. Petersburg, 2007) [in Russian].
2. Bates, R., Determination of pH: Theory and Applications, New York: Wiley, 1964.
3. E. I. Gagarina, N. N. Matinyan, G. A. Kasatkina, and L. S. Schastnaya, Soils and the Soil Cover of the Northwest of Russia (Izd. SPbGU, St. Petersburg, 1995) [in Russian].
4. Classification and Diagnostic System of Russian Soils (Oikumena, Smolensk, 2004) [in Russia].
5. Yu. A. Kokotov, “On the quantitative description of soil acidity,” Pochvovedenie, No. 11, 37–49 (1981).