Bambrough, Renford
Methuen, 1969
Buku Teks
Raz, Joseph
Princeton University Press , 1990
Buku Teks
Christopher, Robert C.
Charles E. Tuttle, 1983
Buku Teks
Plumwood, Val, author
Routledge, 2002
Buku Teks
Salk, Jonas, author
Columbia University Press, 1983
Buku Teks