Hughes, B. B., & Johnston, P. D. (2005). Sustainable futures: Policies for global development in a global knowledge society. Futures, 37(8), 813–831. https://doi.org/10.1016/j.futures.2005.01.017
United States National Intelligence Council (US NIC). 2004. Mapping the Global Future: Report of the National Intelligence Council’s 2020 Project. Washington, DC: United States National Intelligence Council.
Hughes, Barry B. 2004. "The Base Case of International Futures (IFs): Comparison with Other Forecasts." Working papers 2004.04.17. Pardee Center for International Futures, Josef Korbel School of International Studies, University of Denver, Denver, CO.