1. http://www3.epa.gov/climatechange/ghgemissions/sources/electricity.html.
2. http://www.ren21.net/GSR2014-Renewables-2014-Global-Status-Report-Key-Findings-EN.
3. Fundamentals of solar cells: Photovoltaic Solar Energy Conversion, edited by Alan Fahrenbruch and Richard H. Bube, Academic Press, Cambridge, 1983.
4. http://www.pvtech.org/news/back_contact_hit_solar_cell_from_panasonic_pushes_efficiency_record_to_25.6.
5. Photovoltaic materials, history, status and outlook