White, Leonard D., author
Macmillan, 1951
Buku Teks
Naerssen, Frits Herman van, author
E.J. Brill, 1977
Buku Teks
Simon, Herbert A., author
Macmillan, 1955
Buku Teks
Simon, Herbert A., author
Macmillan, 1961
Buku Teks
Toynbee, Arnold J., author
Oxford University Press, 1948
Buku Teks