De Blij, Harm J., author
John Wiley & Sons, 1994
Buku Teks
De Blij, Harm J., author
John Wiley & Sons, 1997
Buku Teks
edited by Fred E. Dohrs and Lawrence M. Sommers
Thomas Y. Crowell, 1969
Buku Teks
Griffin, Paul F., author
Fearon, 1965
Buku Teks
Israel, Saul, author
Holt, Rinehart and Winston, 1976
Buku Teks