1. Gary Kleck and Marc Gertz, "Armed Resistance to Crime: The Prevalence and Nature of Self-Defense with a Gun", 86 Journal of Criminal Law and Criminology 1, 1995. Available at http://www.guncite.com/gcdgklec.html
This is a well known study by Gary Kleck, Florida State University criminologist.
2. National Research Council (2004). Firearms and Violence: A Critical Review. Washington, D.C.: The National Academies Press. Available at http://www.nap.edu/openbook.php?record_id=10881&page=R1
A CNN article says about this literature review from the National Academy of Sciences, "Researchers could not identify a single [gun] regulation that reduced violent crime, suicide or accidents." http://articles.cnn.com/2011-01-18/o...?_s=PM:OPINION
I don't pretend to have read, much less understand, all of the above.