1. Ahmed M (1996) Petrology of Oligocene coal, makum coalfield, Assam, Northeast India. Int J Coal Geol 30:319–325
2. ASTM (1991) Annual book of ASTM standards, section 5, petroleum products, lubricants and fossil fuels, volume 05.05 gaseous fuels, coal and coke, D 2797: Standard practice for preparing coal samples for microscopical analysis by reflected light., pp 308–310
3. ASTM (2013) Annual book of ASTM standards; gaseous fuels; coal and coke; bioenergy and industrial chemicals from biomass. Standard test method for gross calorific value of coal and coke. Vol. 05.06
4. Baruah BP, Khare P (2007) Desulphurization of oxidized Indian coals with solvent extraction and alkali treatment. Energy Fuels 21(4):2156–2164
5. Baruah BP, Saikia BK, Kotoky P, Rao PG (2006) Aqueous leaching on high sulphur subbituminous coals, in Assam. Energy Fuels 20:1550–1555