Kumar, Ranjit
SAGE, 2014
Buku Teks
Gomm, Roger
Palgrave McMillan, 2004
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Paul M. Camic, Jean E. Rhodes, Lucy Yardley
APA, 2007
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Neuman, William Lawrence, 1950-
Allyn and Bacon, 2000
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Greenstein, Theodore N.
Sage Publications, 2001
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