1. EIA. Saudi Arabia country analysis briefs. Washington, DC: Energy information administration, US Department of Energy; 2007. Retrieved from 〈http://www.eia.gov〉.
2. EIA. Independent statistics and analysis. Retrieved October 12, 2014, from U.S. Energy information administration; 2001. Retrieved from 〈http://www.eia.gov〉.
3. German Technical Cooperation (GTZ). Saudi Arabian national transportation study (SANTRAPLAN3). Prepared for ministry of economy and planning, Saudi Arabia; 2004.
4. UN DESA. World Urbanization Prospects: The 2014 Revision. Population division, department of economic and social affairs, United Nations Secretariat; 2014.
5. World Bank. The World Bank databank, world development indicators and global development finance, Saudi Arabia. World Bank; 2016. Retrieved from 〈http://databank.worldbank.org〉.