1. Yudovich, Ya.E. and Ketris, M.P., Neorganicheskoe veshchestvo uglei (The Inorganic Substance of Coals), Yekaterinburg: Ural Branch Russ. Acad. Sci., 2002.
2. Mironov, K.V., Spravochnik geologa-ugol’shchika (Handbook for Coal Miner Geologist), Moscow: Nedra, 1991.
3. Kizil'shtein, L.Ya., Dubov, I.V., Shpitsgluz, A.L., and Parada, S.P., Komponenty zol i shlakov TES (Components of Ashes and Slags for Thermal Power Plants), Moscow: Energoatomizdat, 1995.
4. Drozhzhin, B.S., Shpirt, M.Ya., Danilin, L.D., Kuvaev, M.D., Pikulin, I.V., Potemkin, G.A., and Redyushev, S.A., Solid Fuel Chem., 2008, vol. 42, no. 2, p. 107. https://doi.org/10.3103/S0361521908020110
5. Vassilev, S.V. and Vassileva, C.G., Energy Fuels, 2005, vol. 19, no. 3, p. 1084. https://doi.org/10.1021/ef049694d