1. ASTM D388–12. (2012). Standard classification of coals by rank. Pennsylvania: ASTM International.
2. ASTM D-720/D720M-15. (2015). Standard test method for free-swelling index of coal. Pennsylvania: ASTM International.
3. BIS IS 1350-1. (2003). Methods of test for coal and coke, part I: Proximate analysis (2nd revision). New Delhi: Bureau of Indian Standards.
4. BIS IS 1353. (1993). Methods of test for coal carbonization–caking index, swelling number and (LT) Gray-King assay. New Delhi: Bureau of Indian Standards.
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