1. Automated Power Exchange (APX), 2000. APX California Markets, www.apx.com/ca/GreenPrice1999.htm.
2. AWEA, 1999. How a national Renewables Portfolio Standard would affect utilities, www.awea.org.
3. BMWi, 1999. Bundesministerium für Wirtschaft “Energie Daten 1999”. Bonn.
4. A Powerful opportunity, Making Renewable Electricity the Standard;Clemmer,1999
5. Danish Energy Agency, 1999. The Electricity Reform. Copenhagen.