Belshaw, Cyril S., author
Royal Institute of International Affairs, 1950
Buku Teks
Grattan, C. Hartley
The University of Michigan Press, 1963
Buku Teks
Solem, Alan
Field Museum of Natural History, 1976
Buku Referensi
Forbes, W. Cameron
Houghton Mifflin, 1928
Buku Teks
Alberts, A.
The University of Massachusetts Press, 1983
Buku Teks