Ruse, Michael, author
Cambridge University Press, 2012
Buku Teks
Richardson, W. Norman, author
Macmillan, 1976
Buku Teks
Boyden, Stephen, author
Oxford University Press, 1993
Buku Teks
Ouspensky, P.D.
Hodder and Stoughton, 1957
Buku Teks
Starr, Cecie, author
Thomson, 2004
Buku Teks