http://www.cbsnews.com/news/san-bernardino-shooting-assault-weapon-is-common-denominator-in-mass-shootings/
http://www.pbs.org/wgbh/pages/frontline/government-elections-politics/how-conservatives-reinvented-the-second-amendment/
http://smartgunlaws.org/gun-laws/policy-areas/classes-of-weapons/large-capacity-magazines/
https://ucr.fbi.gov/crime-in-the-u.s/2011/crime-in-the-u.s.-2011/offenses-known-to-law-enforcement/expanded/expanded-homicide-data