Armstrong, Kenneth A.
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eBooks
Maddex, Robert L.
London: Routledge, 1995,
Buku Referensi
Gibson, William M.
Duke University Press, 1948
Buku Teks
editors, A. Barav, D.A. Wyatt, ; asisten editor, Joan Wyatt
Clarendon Press, 1989
Buku Referensi
Botenga, Marc
2007
Artikel Jurnal