Fiadjoe, Albert K.
Cavendish Publ Ltd, UK, 2004
Buku Teks
Blau, Peter M., author
Routledge & Kegan Paul, 1966
Buku Teks
Lynch, Richard M.
McGraw-Hill, 1983
Buku Teks
Kohls, Richard L.
New York, N.Y. Macmillan c.1972,
Buku Teks
Boyd Jr., Harper W.
Richard D. Irwin Inc , 1958
Buku Teks