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Majalah, Jurnal, Buletin
Queensland : The University of Queensland Press, 1985
Majalah, Jurnal, Buletin
Aristotle
Modern Library, 1943
Buku Teks SO
Faculty of international studies, Prince of Songkala university,
Majalah, Jurnal, Buletin
Schlesinger, Arthur Meier
Houghton Mifflin, 1962
Buku Teks SO