- The World Factbook, published by the U.S. Central Intelligence Agency, provides concise factual information on countries around the world, including their capital cities.
- The CIA Factbook Atlas, which contains detailed maps of the world and information on countries, including their capital cities.
- The United Nations website provides information on countries and their capital cities.
- Wikipedia, the free encyclopedia, provides comprehensive information on a wide range of topics, including countries and their capital cities.
- Encyclopedia Britannica, a reputable source for comprehensive and scholarly information, provides detailed articles on countries and their capital cities.
- Geographic dictionaries or encyclopedias, which provide detailed geographic information on countries, including their capital cities.