Sellman, Roger Raymond, author
Edward Arnold, 1954
Buku Referensi
by the Economist Intelligence Unit and the Cartographic Dept. of the Clarendon Press
Oxford University Press, 1956
Buku Referensi
Seton-Watson, R.W., author
Norton, 1972
Buku Teks
Linebarger, Paul Myron Anthony, 1913-1966, author
York D van Nostrand, 1954
Buku Teks
Stocholm, 1958
Buku Teks