Cita APA (7th ed.)
de Blij, H. J., & Birdsall, S. (1974). Essential of geography: Regions and concets. John Wiley.
Cita Chicago (17th ed.)
de Blij, Harm J., i Stephen Birdsall. Essential of Geography: Regions and Concets. New York: John Wiley, 1974.
Cita MLA (9th ed.)
de Blij, Harm J., i Stephen Birdsall. Essential of Geography: Regions and Concets. John Wiley, 1974.
Atenció: Aquestes cites poden no estar 100% correctes.