1. Energy in Brief: What is the Role of Coal in the United States?http://www.eia.gov/energy_in_brief/article/role_coal_us.cfm
2. Chinahttp://www.eia.gov/countries/cab.cfm?fips=CH
3. Indiahttp://www.eia.gov/countries/cab.cfm?fips=IN
4. Monthly Energy Review October 2013http://www.eia.gov/totalenergy/data/monthly/pdf/sec12_9.pdf
5. Coal combustion residues—environmental implications and recycling potentials