1. Biotekhagro—fertilizers based on humic acids, Gumat 80. http://www.biotechagro.ru/products/gumat. php. Accessed November 30, 2016.
2. Vodyanitskii, Yu.N., Tyazhelye metally i metalloidy v pochvakh (Heavy Metals and Metalloids in Soils), Moscow, 2008.
3. Potassium humate: manufacturing and sale. http:// www.gumat.ru. Accessed November 30, 2016.
4. Evdokimova, G.A., Zenkova, I.V., and Pereverzev, V.N., Biodinamika protsessov transformatsii organicheskogo veshchestva v pochvakh Severnoi Fennoskandii (Biodynamics of Organic Matter Transformation in Northern Fennoscandia Soils), Apatity, 2002.
5. Kadulin, M.S. and Koptsik, G.N., Emission of CO2 by soils in the impact zone of the Severonikel smelter in the Kola subarctic region, Eurasian Soil Sci., 2013, vol. 46, no. 11, p. 1107.