Levin, Harvey J.
Rinehard & Comp, Inc , 1959
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Levin, Harvey J.
The John Hopkins Press,, 1971
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Perry, Richard J.
Prentice-Hall, 2003
Buku Teks SO
Sage Publications, 1977
Buku Teks SO
Harper, J. Russell.
University of Toronto Press , 1966
Buku Teks SO