1. Abadie, A., & Gardeazabal, J. (2003). The economic costs of conflict: A Case Study for the Basque Country. American Economic Review, 93(1), 113–132.
2. Brady, H. E., & Collier, D. (2004). Rethinking Social Inquiry: Diverse tools, shared standards. Berkeley: Rowman & Littlefield and Berkeley Public Policy Press.
3. Collier, D., Brady, H. E., & Seawright, J. (2004). Sources of leverage in causal inference: Toward an alternative view of methodology. In H. Brady & D. Collier (Eds.), Rethinking social inquiry: Diverse tools, shared standards (pp. 229–266). Berkeley: Rowman & Littlefield and Berkeley Public Policy Press.
4. Collier, D., & Mahon, J. E., Jr. (1993). Conceptual ‘stretching’ revisited: Adapting categories in comparative analysis. American Political Science Review, 87, 845–855.
5. Drakos, K. (2009). Security economics: A guide for data availability and needs. Economics of Security Working Paper 6, Berlin: Economics of Security. Retrieved July 29, 2011 from https://www.diw.de/documents/publikationen/73/diw_01.c.94892.de/diw_econsec0006.pdf .