Phillips, Richard, 1965-, author
Sage, 2012
Buku Teks
Goodall, Brian, author
Penguin Books, 1987
Buku Referensi
Peter Daniels [and others]
Prentice-Hall, 2001
Buku Teks
De Blij, Harm J., author
John Wiley & Sons, 1977
Buku Teks
De Blij, Harm J., author
John Wiley & Sons, 1995
Buku Teks