1. Ahmed, M. (1996) Petrology of Oligocene Coal, Makum coalfield, Assam, Northeast India, Int. Jour. Coal Geol, v.30, pp.319–325.
2. Ahmed, M. (1989) Characters of Tertiary coal of Makum coalfield, northeast India and its utilization prospects and constraints, 28th Int. Geol. congr., Washington, DC, Abstr. v.3, pp.21–22.
3. Ahmed, M. and Bharali, D. (1984) Petrographic characters of Tertiary coals, Nangalbibra, West Daranggiri coalfield, Garo hills, Meghalaya, Proc. 4th Geophytol. Conf., Lucknow, pp.242–245.
4. Boruah, R.K., Saikia, B.K., Baruah, B.P. and Dey, N.C. (2008) X-ray scattering study of the average polycyclic aromatic unit in Ledo Coal. Jour. Appld. Cryst., v.41, pp.27–30.
5. Bertrand, P.R. (1989) Microfacies and petroleum properties of coals as revealed by a study of North Sea Jurassic coals, Int. Jour. Coal Geol., v.13, pp.575–595.