Holm, Poul, "Viking Dublin and the City-State Concept: Parameters and Significance of the Hiberno-Norse Settlement" (Respondent: Donnchadh Ó Corráin), in Mogens Herman Hansen (ed.), A Comparative Study of Thirty City-State CulturesArxivat 21 June 2013[Date mismatch] a Wayback Machine.. Denmark: Special-Trykkeriet Viborg. (University of Copenhagen, Polis Center). 2000. pp. 251–62.
"Foreign Operations, Export Financing, and Related Programs, Volume 2." United States Congress House Committee on Appropriations. Subcommittee on Foreign Operations, Export Financing, and Related Programs. April 15, 1992. Page 239: "The Republic of Djibouti is in effect a city - state, with few natural resources, few trained workers, no permanent streams and very little arable land. Some 75% of the population live in the capital city, the economy of which is focused on the port, airport, railway, the French garrison, and the re-export of consumer goods."
«Capital Facts for Hong Kong» (en anglès americà). World's Capital Cities, 16-09-2020. Arxivat de l'original el 2021-04-23. [Consulta: 15 octubre 2020].
Holm, Poul, "Viking Dublin and the City-State Concept: Parameters and Significance of the Hiberno-Norse Settlement" (Respondent: Donnchadh Ó Corráin), in Mogens Herman Hansen (ed.), A Comparative Study of Thirty City-State CulturesArxivat 21 June 2013[Date mismatch] a Wayback Machine.. Denmark: Special-Trykkeriet Viborg. (University of Copenhagen, Polis Center). 2000. pp. 251–62.
«Capital Facts for Hong Kong» (en anglès americà). World's Capital Cities, 16-09-2020. Arxivat de l'original el 2021-04-23. [Consulta: 15 octubre 2020].