APA (7th ed.) Zitazioa
United Nations Postal Administration. Postal Issues of the United Nations 1951-1986.
Chicago Style (17th ed.) Zitazioa
United Nations Postal Administration. Postal Issues of the United Nations 1951-1986.
MLA (9th ed.) Zitazioa
United Nations Postal Administration. Postal Issues of the United Nations 1951-1986.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.