Cameron, Silver Donald, author
McClelland and Stewar, 1978
Buku Teks
Edwards, Edward, author
Routledge/Thoemmes Press, 1996
Buku Referensi
UK : The Association of Commonwealth Universities, 1988,
Buku Referensi
Hubbard, G. E., author
International Secretariat Institute of Pasific Relations , 1943
Buku Teks
The British Academy
Oxford University Press, 1985
Buku Referensi