Heyworth, Rex
Macmillan, 1987
Buku Teks
Goates, J. Rex.
Harcourt Brace Jovanovich, 1981
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Miller, G. Tyler (George Tyler), 1931-
Wadsworth, 1991
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Will, John W.
Prentice-Hall, 2002
Buku Teks
Cracolice, Mark S.
Thomson, Brooks/Cole, 2007
Buku Teks