http://en.wikipedia.org/wiki/Nicolaus_Copernicus
http://www-history.mcs.st-andrews.ac.uk/Mathematicians/Copernicus.html
http://www.blupete.com/Literature/Biographies/Science/Copernicus.htm
http://www.phy.bg.ac.yu/web_projects/giants/copernicus.html
http://www.frombork.art.pl/Ang02.htm
http://csep10.phys.utk.edu/astr161/lect/retrograde/copernican.html