Brown, A.J., author
George Allen & Unwin, 1951
Buku Teks
Wicksteed, Philip Henry, 1844-1927, author
Augus M. Kelley, 1950
Buku Teks
Mill, John Stuart
Colonial Press, 1898
Buku Klasik
edited by James H. Weaver
Allyn and Bacon, 1973
Buku Teks
Connecticut JAI Press , 1992
Buku Teks