Barraclough, Geoffrey, 1908-1984, author
Penguin Books, 1967
Buku Teks
Burickson, Sherwin, author
Philosophical Library, 1959
Buku Referensi
Keylor, William R., 1944-, author
Oxford University Press, 1996
Buku Teks
Grenville, J.A.S., author
Routledge, 2005
Buku Teks
Palmer, Alan, author
Penguin Books , 1987
Buku Referensi