Thomas, Henry
The Blakiston Company, 1946
Buku Teks
Christensen, Kit R., author
McGraw-Hill, 2002
Buku Teks
edited by F.S.C. Northrop
Yale University Press, 1949
Buku Teks
Iannone, A. Pablo, author
Routledge, 2001
Buku Referensi
Reader in Philosophy, University of The Panjab, 1965
Buku Teks