Backman, Fredrik, author
Noura Books, 2016
Buku Teks
Teresa Stoppani, Giorgio Ponzo, George Themistokleous.
Routledge, 2017
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Artikel Jurnal
Chalmers, A.F., author
University of Green Sland Press, 1982
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Trese, Leo J., author
Notre Dame, 1964
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