Luis, please read the following two reviews and write your own summary (with references from the reviews).
http://aje.oxfordjournals.org/content/180/2/140.short
http://www.nature.com/nmeth/journal/v6/ ... .1351.html
Write two pages (double space) for each article. Post the working summary that you have by Thursday, July 31, 2014. I will give you some feedback.