Martin, Angus
Lansdowne, 1971
Buku Teks
Harrison, Roy M., author
Whitstable Litho, 1982
Buku Teks
Crawford, Martin
Tata McGraw-Hill, 1976
Buku Teks
Clark, R.B., author
Clarendon Press, 1986
Buku Teks
Davenport, S.J.
Washington, DC: United States Department of the Interior, 1954
Buku Teks