Pile, Steve, author
Routledge, 1996
Buku Teks
De Blij, Harm J., author
John Wiley & Sons, 1977
Buku Teks
Valentine, Gill, author
Prentice-Hall, 2001
Buku Teks
Barcus, Holly R., author
Routledge, 2018
Buku Teks
De Blij, Harm J., author
John Wiley & Sons, 1995
Buku Referensi