Purkitt, H. E. (2007). Annual editions: World politics 06/07 (27th ed.). McGraw-Hill Contemporary Learning Series.
Cita Chicago (17th ed.)Purkitt, Helen E. Annual Editions: World Politics 06/07. 27th ed. Dubuque, Iowa: McGraw-Hill Contemporary Learning Series, 2007.
Cita MLA (8th ed.)Purkitt, Helen E. Annual Editions: World Politics 06/07. 27th ed. McGraw-Hill Contemporary Learning Series, 2007.
Atenció: Aquestes cites poden no estar 100% correctes.