Keller, Suzanne, author
Random House, 1968
Buku Teks
Perkin, Harold
Routledge, 1996
Buku Teks
Mosca, Gaetano, author
McGraw-Hill Book, 1939
Buku Teks
Meisel, James H.
Greenwood Press, 1958
Buku Teks
Bottomore, Tom B., author
Penguin Books, 1964
Buku Teks