Eric S. Belsky, Christopher E. Herbert, Jennifer H. Molinsky, editors
Brookings Institution Press, 2014
Buku Teks
Vercelloni, Matteo
Edizioni L'archivolto, 1996
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Heinz GaÌ?rtner, Adrian Hyde-Price, Erich Reite, editor
Lynne Rienner Publishers, 2000
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Frederick A. Preager, 1966
Buku Teks SO
edited by Karl Cordell
Routledge, 1999
Buku Teks SO