De Blij, Harm J., author
Northwestern University Press, 1968
Buku Teks
Banton Michael, author
Oxford University Press, 1957
Buku Teks
Artikel Jurnal
Estell, Kenneth
Visible Ink Press, 1994
Buku Teks
by Colin M. Turnbull
Simon and schuster, 1962
Buku Teks