Lendrum, Tony
McGraw-Hill, 1995
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Young, Arthur
Sphere, 1986
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Olsen, George H.
Prentice-Hall, 1980
Buku Referensi
Heiserman, David L.
Prentice-Hall, 1981
Buku Referensi
Williams, Carolyn L.
American Psychological Association , 2011
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