Here's the NYT article mentioned. It includes a link to estimate research by the author cited in the article.
http://www.nytimes.com/2012/04/03/science/civil-war-toll-up-by-20-percent-in-new-estimate.html?_r=2&pagewanted=all%3Fsrc%3Dtp&smid=fb-share
To access the article, readers need to copy and paste the entire URL in their address bar.