Lincoln, Yvonna S.
SAGE Publications, 1985
Buku Teks
Friedl, Alfred E
McGraw-Hill, 2001
Buku Teks
Friedl, Alfred E.
McGraw-Hill, 2001
Buku Teks
Graziano, Anthony M.
Pearson Education, 2014
Buku Teks
Pertti J, Pelto
Cambridge University Press, 2012
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