1. 8. “Hydrogen from Coal—Future Technologies” (Offce of Fossil Energy, U.S. Department of Energy, Washington, DC, 2007); www.fossil.energy.gov/programs/fuels (accessed January 2008).
2. 2. The Future of Coal—Options for a Carbon-Constrained World (Massachusetts Institute of Technology, Cambridge, MA, 2007); http://web.mit.edu/coal (accessed January 2008).
3. 6. “What is Gasifcation?” (Gasifcation Technologies Council, Arlington, VA, 2007); www.gasifcation.org/Technology.htm (accessed January 2008).
4. 1. The Coal Resource—A Comprehensive Overview of Coal (World Coal Institute, Richmond-upon-Thames, UK, 2005); www.worldcoal.org/assets_cm/fles/PDF/thecoalresource.pdf (accessed January 2008).