http://battleofkursk.org/
http://www.historylearningsite.co.uk/causes_world_war_two.htm
http://www.historyonthenet.com/WW2/causes.htm
http://www.ushmm.org/wlc/en/article.php?ModuleId=10005143
http://www.ushistory.org/us/51e.asp
http://www.gwu.edu/~nsarchiv/NSAEBB/NSAEBB162/index.htm