Gaunt, Jeremy
Our world now : Reuters
Thames & Hudson, 2010
 Buku Referensi
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
Inventors and discoverers : changing our world
National Geographic Book Service
National Geographic Society, 1988
 Buku Referensi
Ewing, Ethel E.
Our widening world : a history of the world's peoples
Rand McNally & Company, 1962
 Buku Teks