1. ASTM Standard D2013/D2013M – 12; Standard Practice for Preparing Coal Samples for Analysis;ASTM International,2013
2. ASTM Standard D7582 – 12; Standard Test Methods for Proximate Analysis of Coal and Coke by Macro Thermogravimetric Analysis;ASTM International,2013
3. ASTM Standard D4239 – 12; Standard Test Method for Sulfur in the Analysis Sample of Coal and Coke using High-Temperature Tube Furnace Combustion;ASTM International,2013
4. Fossil in situ spores and pollen grains: an annotated catalogue;Balme;Rev. Palaeobot. Palynol.,1995
5. Geochemistry and petrology of selected coal samples from Sumatra, Kalimantan, Sulawesi, and Papua, Indonesia;Belkin;Int. J. Coal Geol.,2009