Dyfyniad APA
de Blij, H. J., & Birdsall, S. (1988). Essential of geography: Regions and concets (5th ed.). John Wiley.
Dyfyniad Arddull Chicago
de Blij, Harm J., and Stephen Birdsall. Essential of Geography: Regions and Concets. 5th ed. New York: John Wiley, 1988.
Dyfyniad MLA
de Blij, Harm J., and Stephen Birdsall. Essential of Geography: Regions and Concets. 5th ed. John Wiley, 1988.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.