Shuman, Howard E.
Prentice-Hall, 1992
Buku Teks
Sorauf, Frank J.
Glenview, Ill. Scott Foresman and Co, 1988.,
Buku Teks
West, Katharine
F.W. Cheshire, 1965
Buku Teks
Pethybridge, Roger
Frederick A. Praeger, 1962
Buku Teks
Sage Publications 1993, 1993
Buku Teks