Austin, Dennis
Routledge , 1922
Buku Teks
Cowen, Zelman, author
North-Western University Press, 1965
Buku Teks
The Association of Commonwealth Universities,
Buku Referensi
Association of Commonwealth Universities, 1976
Buku Teks
Millar, T.B.
Sydney University Press, 1967
Buku Teks