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Buku Teks
Kirsh, Steven J., author
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Buku Teks
Crenshaw, Nadine
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Buku Teks
Sorenson, Herbert, author
McGraw-Hill, 1971
Buku Teks
Hubbard, L. Ron, 1911-1986, author
The Way to Happiness Foundation International, 2007
Buku Teks