‘Trends in American values 1987-2012’, The Pew Research Center, 4 June 2012.
Victor Asal and Amy Pate, ‘The decline of ethnic political discrimination, 1950-2003’, in Monty G. Marshall and Ted Robert Gurr (eds) Peace and Conflict 2005, College Park, MD: Center for International Development & Conflict Management, University of Maryland, 2005, p. 38.
Peter Brecke's 'Conflict Catalogue'
Audrey Cronin, How Terrorism Ends: Understanding the Decline and Demise of Terrorist Campaigns.
Jim Oeppen and James W. Vaupel, ‘Broken limits to life expectancy’, Science, 296, 5579 (2002)