Moore, G.E.
Routledge & Kegan Paul, 1958
Buku Teks
Gomperz, Heinrich, author
Christopher Pub. House, 1953
Buku Teks
George allen & Unwin, ltd, 1948
Buku Teks
Tran, Van Doan, author
The council for research in values and philosophy, 2001
Buku Teks
Mansell, 1992
Buku Referensi