1. US Department of Energy, National Center for Photovoltaics, PF Roadmap Workshop, Chicago, IL, June 22–25, 1999.
2. US Department of Energy, National renewable energy laboratory, Photovoltaics energy for the new millennium, The National 2000–2004 Photovoltaics Program Plan, January 2000.
3. PV News, P. Maycock (Ed.), February 2001.
4. N. Yuge, H. Baba, F. Aratani, Method and apparatus for purifying silicon, US Patent 5,182,091, January 26, 1993.