Willard, Wendy
Osborne/McGraw-Hill, 2001
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Hirooka, Kyushi
PT Elex Media Komputindo, 2019
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Soyinka, Wale
McGraw-Hill, 2012
Buku Teks SO
Shipps, Steve
Blackwell Publishing, 2008
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Brannan, James A.
McGraw-Hill, 2011
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