De Blij, Harm J.
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.
McGraw-Hill, 2012
Buku Teks
by Jerome D. Fellmann, Mark D. Bjelland, Arthur Getis, Judith Getis
McGraw-Hill, 2010
Buku Teks
Knapp, Brian
Longman House, 1992
Buku Teks