De Blij, Harm J., author
John Wiley & Sons, 1995
Buku Referensi
De Blij, Harm J., author
John Wiley & Sons, 1977
Buku Teks
edited by R.J. Johnston, Derek Gregory, Geraldine Pratt, Michael Watts
Blackwell Publishing, 2000
Buku Referensi
Malinowski, Jon C., author
McGraw-Hill, 2012
Buku Teks
by Jerome D. Fellmann, Mark D. Bjelland, Arthur Getis, Judith Getis
McGraw-Hill, 2010
Buku Teks