Inventors and discoverers : changing our world
National Geographic Book Service
National Geographic Society, 1988
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Saaty, Thomas L.
Embracing the future : meeting the challenge of our changing world
Praeger, 1990
 Buku Teks SO
Our world's heritage
National Geographic Book Service.
National Geographic Society, 1987
 Buku Referensi
Kolevzon, Edward R.
Our world and its people
Allyn and Bacon, 1959
 Buku Teks SO
Gaunt, Jeremy
Our world now : Reuters
Thames & Hudson, 2010
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