Rothstein, Andrew, author
Penguin Books , 1950
Buku Teks
Mongait, Alexander, author
Foreign Languages Publishing House, 1959
Buku Teks
Munich : Institute for the Study of the USSR
Majalah, Jurnal, Buletin
by the Economist Intelligence Unit and the Cartographic Dept. of the Clarendon Press
Oxford University Press, 1956
Buku Referensi
Hammer, Darrel P.
Westview Press, 1990
Buku Teks