by the Economist Intelligence Unit and the Cartographic Dept. of the Clarendon Press
Oxford University Press, 1956
Buku Referensi
Department of Films and Pub, 1961
Buku Teks
Knippenberg, Hans
SUN, 1988
Buku Teks
edited by Roger Goodman
Cambridge University Press, 2002
Buku Teks
Heilbroner, Robert L., author
Harper & Row , 1963
Buku Teks