1. Agrochemical Methods of Soil Studies, Ed. by A.V. Sokolov (Nauka, Moscow, 1975) [in Russian].
2. E. V. Vanchikova, Chemical Metrology and Quality Control in the Quantitative Chemical Analysis. Part 1. Characterization of Errors of the Results of Quantitative Chemical Analysis (Syktyvkar, 2010) [in Russian].
3. GOST (State Standard) 26484-85: Method of Determining Exchangeable Acidity of Soils (Izd. Standartov, Moscow, 1985) [in Russian].
4. GOST (State Standard) 8.207-76: Direct Measurements with Multiple Observations. Methods to Treat the Results of the Observations (Standartinform, Moscow, 2006) [in Russian].
5. GOST R (Russian State Standard) 8.563-2009: State System for Ensuring the Uniformity of Measurements. Methods of Measurements (Standartinform, Moscow, 2010), p. 33 [in Russian].