Wolff, Robert Lee, author
Harvard University Press, 1956
Buku Teks
Baruch, Bernard M.
Sinmon and Schuster, INC, 1954
Buku Teks
Uehiro, Eiji
Charles E.Tuttle Company , 1998
Buku Teks
Artikel Jurnal
Sachs, Jeffrey D., author
Penguin Books, 2005
Buku Teks