De Blij, Harm J., author
John Wiley & Sons, 1997
Buku Teks
by A.D. Cliff ... [and others]
Oxford University Press, 2010
Buku Teks
De Blij, Harm J., author
John Wiley & Sons, 1981
Buku Teks
Margai, Florence M., author
Earthscan , 2010
Buku Teks
edited by Sybil P. Parker
McGraw-HIll, 1995
Buku Referensi