Biographical dictionary of twentieth-century philosophers
edited by Stuart Brown, Diane Collinson, Robert Wilkinson
Roudledge, 1996
 Buku Referensi
Teed, Peter
A dictionary of twentieth century history 1914-1990
Oxford University Press , 1992
 Buku Referensi
Cohen, John Michael, 1903-1989
The Penguin dictionary of twentieth-century quotations
Viking, 1993
 Buku Referensi
Reese, Trevor R.
Australia in the twentieth century : a political history
F.W. Cheshire, 1964
 Buku Teks SO
Brecht, Arnold
Political theory: the foundations of twentieth-century political thought
Princenton University Press, 1968
 Buku Teks