by Charles R. Landau
(in the bottom of the page)
by Autodesk Sustainability workshop
by the Department of Mechanical Power Engineering and Energy, Minia University, Egypt.
Note that it can also be applied to inclination of solar panels, solar hot air collectors, etc.
DIY solar panels, Part II
http://www.catskillhouse.us/blog/diy-solar-panels-part-ii/
by Homeowner's Blog - Home improvement with an eye toward sustainability
DIY solar panels, Part I
by Energy Boom.