1. Wikipedia http://en.wikipedia.org/wiki/Special:Search? search=solar+Radiation&go=Go, state 07.12.2007
2. R. H. B. Exell “The Intensity of Solar Radiation”, King Mongkut's University of Technology Thonburi, 2000 http://www.jgsee.kmutt.ac.th/exell/Solar/Intensity.html
3. ASHRAE Handbook, Fundamentals Volume, Chapter 30 “Fenestration”, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., Atlanta, GA 2001
4. A modification of the ASHRAE clear sky model;Machler;ASHRAE Trans,1985