1. Alastuey A, Jiménez A, Plana F, Querol X, Suárez-Ruiz I (2001) Geochemistry, mineralogy, and technological properties of the main Stephanian (Carboniferous) coal seams from the Puertollano Basin, Spain. Int J Coal Geol 45:247–265
2. ASTM Standard D2492-02 (2002, Reapproved 2007). Standard test method for forms of sulfur in coal. ASTM International, West Conshohocken, PA
3. ASTM Standard D2797/D2797M-11a (2011) Standard practice for preparing coal samples for microscopical analysis by reflected light. ASTM International, West Conshohocken, PA
4. ASTM Standard D3173–11 (2011) Test method for moisture in the analysis sample of coal and coke. ASTM International, West Conshohocken
5. ASTM Standard D3174–11 (2011) Annual book of ASTM standards. Test method for ash in the analysis sample of coal and coke. ASTM International, West Conshohocken