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Buku Referensi
Soemitro Djojohadikusumo
[publisher not identified], 1975
Buku Teks
Junaidi
Faculty of Humanities University of Indonesia, 2002
Artikel Jurnal
Rollason, Russell G.
Alternative Pub. Cooperative, 1981
Buku Teks SO
Mudie, Robyn
The University of Hull , 1998
Buku Teks SO