1. Adams, W. M. (2006, January 29-21). The Future of Sustainability: Re-thinking Environment and Development in the Twenty-first Century. In Proceedings of the IUCN Renowned Thinkers Meeting. Madrid: The World Conservation Union (IUCN). Retrieved from http://cmsdata.iucn.org/downloads/iucn_future_of_sustainability.pdf
2. Baum, S., & Payea, K. (2005). Education Pays 2005 Update. Washington, DC: College Board. Retrieved from http://www.collegeboard.com/prod_downloads/press/cost05/education_pays_05.pdf
3. Baum, S., Payea, K., & Steele, P. (2006). Education Pays 2006 Second Update. Washington, DC: College Board. Retrieved from http://www.collegeboard.com/prod_downloads/press/cost06/education_pays_06.pdf
4. Introduction;E.Bomberg;The European Union: How Does it Work?,2003