Hodges, Henry
Penguin Press, 1970
Buku Teks
Glover, T. R.
Penguin Books, 1944
Buku Teks
prepared by the Special Publications Division, National Geographic Society, Washington, D.C.
The National Geogarphic Society, 1986
Buku Referensi
Mellersh, H.E.L.
Simon & Schuster, 1994
Buku Referensi
Matthews, Rupert
Miles Kelly, 2007
Buku Teks