Borrie, W.D.
The Australian National University, 1954
Buku Teks
Tampke, Jurgen
New South Wales University Press, 1990
Buku Teks SO
Binion, Rudolph
Elsevier, 1976
Buku Teks
Bocchetta, Vittore E.
Follett Publishing Company, 1987
Buku Referensi
Clark, Martin
Longman, 1998
Buku Teks SO