Gray, Richard, 1944-, author
Lund Humphries, 1996
Buku Teks
Passmore, John, author
Gerald Duckworth, 1957
Buku Teks
Passmore, John, author
Penguin Books, 1972
Buku Teks
Penniman, T.K.
Duckworth, 1935
Buku Teks
Crafton, Donald, author
New York : Macmillan Library reference USA,1997,
Buku Referensi