S. Hayrapetyan, L. Hayrapetyan, L. Mangasaryan, and H. Khachatryan, “ON SORPTION OF POTASSIUM IONS BY MEANS OF SILICA–MANGANESE DIOXIDE SYSTEM”, Proc. YSU B: Chem. Biol. Sci., vol. 49, no. 1 (236), pp. 29–32, Apr. 2015.