Beckingham, C.F.
Macmillan & Co., 1960
Buku Referensi
Lenczowski, George, author
Cornell University Press, 1956
Buku Teks
Routledge, 2015
Buku Teks
Taafe, Robert N.
Washington Frederick A. Praeger, 1965
Buku Teks
Moaddel, Mansoor, author
Oxford University Press, 2017
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