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http://www.suppliers-pv.com/fileadmin/user_upload/2012/pdf/esa12_GW-ES-Screen.pdf
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http://www.pv-power-plants.com/fileadmin/user_upload/pdf/PVPP2012_low_02.pdf
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http://www.ips.gov.au/Category/Educational/The%20Sun%20and%20Solar%20Activity/General%20Info/Solar_Constant.pdf
5. Abdullah, M.O.: Applied Energy: An Introduction. CRC Press, New York (2012)