1. Glembotskii, V.A. and Klassen, V.I., Flotatsionnye metody obogashcheniya (Flotation Methods of Enrichment), Moscow: Nedra, 1981.
2. Kawatra, S.K. and Eisele, T.C., Coal Desulfurization: High-Efficiency Preparation Methods, New York: Taylor and Francis, 2001.
3. Smirnov, V.O. and Bilets’kii, V.S., Flotatsiini metodi zbagachennya korisnikh kopalin (Flotation Methods of Enrichment of Mineral Resources), Donetsk: Skhidnii Vidavnichii Dim, 2010.
4. Shireesha, M., Rama, N., Harini, P., Mounika, A., and Dinesh, K., Recovery of coal by froth flotation equipment, Int. J. Sci.,
Eng. Manage., 2017, vol. 2, no. 3, pp. 75–78.
5. Das, B. and Mohanty, J.K., Mineralogical characterization and beneficiation studies of pyrophyllite from Orissa, India, J. Miner. Mater. Charact. Eng., 2009, vol. 8, no. 4, pp. 329–338.