1. Humus Chemistry: Genesis, Composition, Reactions;Stevenson,1994
2. Feasibility studies for isolation of Humic acid from coal of Mongchen Coalfield, Nagaland;Das;J. Indian Chem. Soc.,2013
3. Characterizations of Humic Acid Isolated from Coals of Two Nagaland Coalfields of India in Relation to their Origin;Das;J. GeolSoc. India,2015
4. A comparative Evaluation on the Oxidative Approach for Extraction of Humic Acids from low rank coal of Mukah, Sarawak;Fong;J. Braz. ChemSoc.,2007