Artikel Jurnal
oleh Rudioro Rochmat... [et.al.]
Pradnya Paramita, 1978
Buku Teks
Oram, Andrew
O'Reilly & Associates, Inc., 1991
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Friedmann, Julian
Intellect, 2000
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Frank C. Wilson, Scott L. Adamson, Trey Cox, Alan E.O'Briyan
Cengage learning, 2013
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